How do I RGB shift?

I need to make a background with a RGB shifting effect. What command would I need to use to make this?

what i got from your question:- you want to make the background change color with parallel to your game

if it is ,simple (but i will have to know what type of shift you want:- linearly from a color to a color or randomly changing the color

1.) create 3 variables ,named r_comp,g_comp,b_comp

2.) make a "system" event with "every tick"

3.) in its action section,go to system and select "change layer background color".

then the dialog box will ask you for the color.In place of red part,write r_comp(the variable you declared earlier).do same thing with green and blue

4.) i don't know which type of shift you want.some shift can be really,really tedious.But one thing is clear,now you have to play with r_comp,g_comp and b_comp.

for example:-i connected r_comp with x_coordinate of the player.as the player does too far,the screen color get much more red.

best of luck