Scale-color Example

to setup
  clear-all                         ; clear all patch and turtle variables
  create-turtles 500 [              ; create 500 turtles in the center of the world
    setxy random-xcor random-ycor   ; place turtles randomly
    set heading 270                 ; face west
    recolor
  ]
  reset-ticks
end 

to go
  ask turtles [
    fd 1
    recolor
  ]
  tick
end 

to recolor  ;; turtle procedure
  ; The turtle sets its color according to its x-coordinate.
  ; As its x-coordinate approaches the left side of the world,
  ; the turtle becomes darker.
  ; As its x-coordinate moves to the right side of the world,
  ; the turtle becomes lighter
  set color scale-color shading xcor min-pxcor max-pxcor
end 


; Public Domain:
; To the extent possible under law, Uri Wilensky has waived all
; copyright and related or neighboring rights to this model.