Color Cycling
Hello. I do not know if it is already implemented in Construct 2, but is present the Color Cycling WebGL Effect? See demo linked
http://www.chromeexperiments.com/detail/canvas-cycle/
http://www.effectgames.com/demos/canvascycle/
or like this "spectrum beam", but that follows a path:
https://www.shadertoy.com/view/XsB3zW