Playing a Wild Draw Color Card on top of another Wild Draw Color Card to get out of drawing cards in UNO FLIP
No, it's not valid to do so since according to the Mattel's UNO FLIP! rules the next player:  


  Wild Draw Color Card (DARK SIDE)
     ... must draw until they get a color of your choosing (no matter how many cards they have to draw to do so) and lose their turn.  
  
  Wild Draw 2 Card (LIGHT SIDE)
    ... must draw two cards from the DRAW pile and lose their turn.  


But for the player after the next player (who had to pick up the cards) it's a valid play.

Note: Stacking or Progressive UNO, i.e. playing a Draw +1/+5 Card on top of another Draw +1/+5 Card without first drawing card is not allowed, but it's a common house rule used by many.


  Draw One / Five Card
  the next player must draw one / five card and miss their turn