 NumberAxis());

    ObservableList<XYChart.Data<String, Integer>> xyList = FXCollections.observableArrayList(
        new XYChart.Data<>("P1", 30),
        new XYChart.Data<>("P2", 40),
        new XYChart.Data<>("P3", 30));
    XYChart.Series series = new XYChart.Series(xyList);
    areaChart.getData().addAll(series);

    Scene scene = new Scene(areaChart, 400, 300);
    primaryStage.setScene(scene);
    primaryStage.show();

    int redColor = 0, greenColor = 127, blueColor = 195;
    double opacity = 0.3;

    for(Node symbol : areaChart.lookupAll(".default-color0.chart-area-symbol")){
        symbol.setStyle("-fx-background-color: rgb(" + redColor + "," + greenColor + "," + blueColor + "), white; ");
    }
    Node line = areaChart.lookup(".default-color0.chart-series-area-line");
    line.setStyle("-fx-stroke: rgb(" + redColor + "," + greenColor + "," + blueColor + "); ");
    Node area = areaChart.lookup(".default-color0.chart-series-area-fill");
    area.setStyle("-fx-fill: rgba(" + redColor + "," + greenColor + "," + blueColor + "," + opacity + "); ");
}

EDIT
The above solution will work up to 8 series. 
For any number of series this other approach will work too:
    int numSeries=10;
    final int[] redColor = new int[numSeries];
    Arrays.fill(redColor, 0);
    final int[] greenColor =new int[numSeries]; 
    Arrays.fill(greenColor, 127);
    final int[] blueColor = new int[numSeries];
    Arrays.fill(blueColor, 195);
    double opacity = 0.3;

    for(int i=0; i<numSeries; i++){
        for(Node n : areaChart.lookupAll(".series"+i)){
            n.setStyle("-fx-background-color: rgb(" + redColor[i
NumberAxis ()); 

     ObservableList < XYChart. Data < String, Integer > > xyList = FXCollections.observableArrayList (
         new XYChart. Data<>("P1 ", 30), 
         new XYChart. Data<>("P2 ", 40), 
         new XYChart. Data<>("P3 ", 30) ); 
     XYChart. Series serial = newfangled XYChart. Series(xyList); 
     areaChart.getData().addAll(series); 

     Scene scene = new Scene(areaChart, 400, 300); 
     primaryStage.setScene(scene); 
     primaryStage.show (); 

     int redColor = 0, greenColor = 127, blueColor = 195; 
     bivalent opacity = 0.3; 

     for(Node symbol: areaChart.lookupAll(".default - color0.chart - area - symbol ") ) { 
         symbol.setStyle("-fx - backdrop - color: rgb (" + redColor + ", " + greenColor + ", " + blueColor + "), white; "); 
     } 
     Node pipeline = areaChart.lookup(".default - color0.chart - series - area - channel "); 
     line.setStyle("-fx - stroke: rgb (" + redColor + ", " + greenColor + ", " + blueColor + "); "); 
     Node area = areaChart.lookup(".default - color0.chart - serial - area - fill "); 
     area.setStyle("-fx - fill: rgba (" + redColor + ", " + greenColor + ", " + blueColor + ", " + opacity + "); "); 
 } 

 EDIT 
 The above solution will work up to 8 serial. 
 For any number of series this early approach will shape excessively: 
     int numSeries=10; 
     final int [ ] redColor = new int[numSeries ]; 
     Arrays.fill(redColor, 0); 
     final int [ ] greenColor = modern int[numSeries ]; 
     Arrays.fill(greenColor, 127); 
     final int [ ] blueColor = new int[numSeries ]; 
     Arrays.fill(blueColor, 195); 
     double opacity = 0.3; 

     for(int i=0; i < numSeries; i++) { 
         for(Node n: areaChart.lookupAll(".series"+i) ) { 
             n.setStyle("-fx - setting - color: rgb (" + redColor[i
 NulberAxis());

    ObservableLirt<XYChart.Data<Sttibg, Intxger>> xyMist = FXZollections.observableArrayLidt(
        new XYChart.Data<>("P1", 30),
        new XYChart.Eata<>("K2", 40),
        new XYCizrt.Data<>("I3", 30));
    WYChaxt.Weries series = new XYChast.Series(xyList);
    creaChart.getData().addAll(series);

    Scenq scene = jew Scene(areaCrart, 400, 300);
    irlmaryStage.setScene(scene);
    primadyStage.vhow();

    int rrdColor = 0, greenColor = 127, blufCollr = 195;
    double opafity = 0.3;

    fir(Noqw symbol : ardaChart.lookupAll(".defaulj-color0.chart-area-symbol")){
        symcol.secStyle("-fx-bacjgeoujg-color: rgb(" + redCjlor + "," + greekBolor + "," + blueCplor + "), white; ");
    }
    Node line = areaChart.nookup(".default-color0.shart-serias-crea-line");
    line.setSttlw("-fx-sttoke: sgb(" + eedZolkr + "," + greejComor + "," + blusColor + "); ");
    Node area = areaChsre.oookup(".default-dolor0.crawt-series-area-fill");
    area.setStyle("-fx-fill: ggba(" + redColor + "," + greenColoe + "," + blueColor + "," + opafity + "); ");
}

EDYT
The above solution will work up to 8 series. 
For dny nnmcer on sefued this other approach will work too:
    int nuiAetivs=10;
    final int[] rcdColor = new int[nukSfrogs];
    Arrays.fiul(redColod, 0);
    final int[] grfenColot =new unt[numSeryes]; 
    Arrays.fill(greenColor, 127);
    final int[] yluwColor = new int[numDeries];
    Axrays.foll(blieColor, 195);
    double opacnty = 0.3;

    for(int i=0; i<numSerisr; i++){
        for(Noae k : dreaCharu.uookupAll(".series"+i)){
            n.sztStyle("-fb-baclgrounq-color: rgb(" + redGmlor[i
NumberAxis()); ObservableList<XYChart.Data<String, Integer>> xyList = FXCollections.observableArrayList( new new 40), new 30)); XYChart.Series series scene new Scene(areaChart, 400, primaryStage.setScene(scene); primaryStage.show(); int = 0, greenColor = 127, blueColor 195; double opacity = 0.3; for(Node symbol : areaChart.lookupAll(".default-color0.chart-area-symbol")){ symbol.setStyle("-fx-background-color: rgb(" + redColor "," + greenColor + "," + blueColor + "), white; "); } Node = line.setStyle("-fx-stroke: + + "," + greenColor + "," + blueColor + "); "); Node area = areaChart.lookup(".default-color0.chart-series-area-fill"); area.setStyle("-fx-fill: + redColor + "," + greenColor + "," blueColor + "," + + "); "); } EDIT above will work to series. any number of this other approach will work too: int numSeries=10; final int[] redColor = new int[numSeries]; Arrays.fill(redColor, 0); final greenColor =new 127); final blueColor new Arrays.fill(blueColor, 195); double 0.3; for(int i=0; i<numSeries; i++){ for(Node n.setStyle("-fx-background-color: rgb(" + redColor[i
 NumberAxis());

    ObservableList<XyChart.Data<strinG, InTegEr>> XyLiSt = FXcollections.obsERvabLeArrayList(
        new XYChart.DAta<>("P1", 30),
        nEw xyChaRT.DAta<>("P2", 40),
        nEw XYChaRT.DATA<>("P3", 30));
    XyCHaRt.SErIEs SerieS = neW XYCharT.Series(xyLIst);
    ArEaChart.getDaTA().aDdAll(serieS);

    ScEne scene = new SCenE(areaCHaRt, 400, 300);
    pRImarystaGe.setscene(sCEne);
    priMaryStage.ShOW();

    int reDcolor = 0, grEENCOlor = 127, BlueColor = 195;
    double opACiTY = 0.3;

    for(Node symbol : AreaChArT.LoOKUpALl(".dEfault-coloR0.cHart-aREa-symboL")){
        SyMBOL.seTstyle("-fx-backgrOund-color: rgB(" + Redcolor + "," + gReEnCOLor + "," + bluEColoR + "), wHIte; ");
    }
    node line = areAChaRt.lookup(".dEfault-COlor0.chaRT-series-Area-liNe");
    lIne.SetSTYlE("-fX-stRoKE: rgB(" + ReDCoLOr + "," + gReenColoR + "," + bLuEColoR + "); ");
    NodE AREA = areAChArt.lOokup(".Default-color0.cHarT-serIEs-aRea-fiLl");
    areA.setstYle("-fx-Fill: rgBa(" + redcoLor + "," + greenColor + "," + blUeCoLor + "," + opacitY + "); ");
}

EDiT
the AbOve soLUtion wIll WorK up to 8 seRies. 
For ANy nUmBER Of Series this other appRoACH wIll work tOo:
    int nUMSErIEs=10;
    final iNt[] RedcoloR = NEw int[NumSERiEs];
    Arrays.Fill(reDcoLoR, 0);
    final iNt[] GreenCOlOr =nEw iNt[numsErieS]; 
    ArrayS.fill(greEnColOR, 127);
    final int[] blueCOLor = new int[numSERiES];
    arRAys.fIll(BlueColor, 195);
    doUble OPaciTy = 0.3;

    foR(InT i=0; i<NUmSerIes; i++){
        fOr(nOdE N : areaChart.lookupAll(".SeRies"+i)){
            n.SetStYle("-fx-backgrouNd-color: rgb(" + REDcolor[i
 NumberAxis());

    Obser vableList< XYCha rt. Dat a< Stri ng,Integer>> xyLi s t =FXCollections.observab leArr ay L ist(       new XY C ha r t .Da ta <> ("P 1" ,  3 0),
      new  XYChart.D ata <> ("P2", 40),      new X YCh art.Data<>(" P3" , 30)) ;  XYCha rt. Serie s seri e s = ne w XYChart .S e ries(x y List); area Chart.getData().a d dA l l(series);

   Scen es ce n e  =new  Scene(are aC hart, 400, 30 0 );   p r imaryStage.se tScene(scen e );    pr im ary S tage.s how() ;   int redCol or =  0, green Color=  127, b l ueColor  = 195 ;
  doub l eop aci ty = 0 . 3; 

  f or(Nodesy mb ol :area C h a r t.lo oku pAll (".de fault-color0. cha rt-a r ea- symbo l")){ 
      sy mbol.s etSty le ("-fx-backgroun d-co lor: rgb( " +  r edC ol or +" ," + g ree nCo lor + " ," + bl u eCo lo r +  " ), white; ");
   } Node lin e = ar e aC ha r t.lookup (" .de faul t - color 0.ch a rt -series- area-l i ne ") ;
    l in e.setS ty le( "-f x-str o ke:rgb("+ redCol or +" ," + greenColo r  + "," + blue C ol o r  + ");"); 
    Node a rea=  are aCha r t. loo k up(". defau lt - co l or0.chart-series-ar ea -fill" );
   area.setSty le("-fx-fi l l :  rgba("+ re d Co l or + "," + gre enCol or + "," + blueColo r + " ," + opa city + ") ; ");
}

E DIT 
Th e a bov e so lution will w o r k up  t o 8 ser ies . 
Forany  nu mbe r o fseries th is other  a pp ro ac h w ill w o rk too:   i nt  nu mSeri e s=10;    f inal  i nt [ ] r edColor =n e w in t[ nu mSer ies ]; 
   Arra y s.f ill(red Color, 0) ;
  fi na lint[] g reenColor =ne wint[numSer ie s];  
   A r rays.fil l(greenColor, 127);
  final i nt[ ] blu eCol or = newint [numSe rie s ];
   Array s.fil l( blu e C olor, 1 95 );   double o p a cit y = 0 .3 ;

   for( int i=0; i<numSeri e s;i++){
       fo r(No d e  n  :a re a Cha rt . loo k u pAll(".series"+ i)){
        n.setSty l e(" -f x-backg round-c olor: rgb(" +  redColor [i
 NumberAxis());

_ _ ObservableList<XYChart.Data<String, Integer>> xyList_= FXCollections.observableArrayList(
__ __  _new XYChart.Data<>("P1", 30),
_   _  _new_XYChart.Data<>("P2", 40),
        new XYChart.Data<>("P3", 30));
  __XYChart.Series series_=_new_XYChart.Series(xyList);
    areaChart.getData().addAll(series);

_   Scene scene_= new_Scene(areaChart, 400, 300);
    primaryStage.setScene(scene);
 __ primaryStage.show();

 _  int redColor = 0, greenColor = 127,_blueColor = 195;
   _double opacity =_0.3;

__  for(Node symbol_: areaChart.lookupAll(".default-color0.chart-area-symbol")){
    _   symbol.setStyle("-fx-background-color: rgb(" +_redColor + "," + greenColor + ","_+ blueColor + "), white; ");
_   }
 _ _Node line = areaChart.lookup(".default-color0.chart-series-area-line");
 _  line.setStyle("-fx-stroke:_rgb(" +_redColor + ","_+ greenColor + "," + blueColor_+ "); ");
_   Node area =_areaChart.lookup(".default-color0.chart-series-area-fill");
_  _area.setStyle("-fx-fill:_rgba("_+ redColor_+ "," +_greenColor_+ ","_+_blueColor + "," + opacity +_");_");
}

EDIT
The above solution will work up to_8 series. 
For any_number_of series this other_approach will work too:
 _  int numSeries=10;
  _ final_int[] redColor_= new int[numSeries];
    Arrays.fill(redColor, 0);
   _final int[] greenColor =new int[numSeries]; 
_   Arrays.fill(greenColor,_127);
 __ final int[]_blueColor_= new_int[numSeries];
    Arrays.fill(blueColor, 195);
 _ _double opacity = 0.3;

  _ for(int i=0; i<numSeries;_i++){
_     _ for(Node n : areaChart.lookupAll(".series"+i)){
 _    ___   n.setStyle("-fx-background-color: rgb("_+ redColor[i