anchor.diff:      real :: hue1,hue2,light1,light2,chroma1,chroma2,lim1,lim2
       integer :: ncolors
       real :: dz
  -    option = ''
  +    option = 'spiral'
       hue1 = 0.0
       hue2 = 360.0
       light1 = 0.0
  
positive.code:             call checkrgb(red,grn,blu,clip)
              call formatrgb(red,grn,blu,rgbstring)
              if (gmt.eq.'none') then
                  write(*,*) trim(rgbstring)
              else
                  c = lim1 + (lim2-lim1)*(i-1)/n
                  if (gmt.ne.'print') then
  
negative.code:             call checkrgb(red,grn,blu,clip)
              call formatrgb(red,grn,blu,rgbstring)
              if (gmt.eq.'none') then
                  write(*,'(A)') trim(rgbstring)
              else
                  c = lim1 + (lim2-lim1)*(i-1)/n
                  if (gmt.ne.'print') then
  