How can I get segments (of different varieties) to change color in a background?

I'm trying to make a background that will consistently change color, using this artwork as a reference (for example, trying to get the colors in the background of the art to slowly change).

download is the image.

Thank you for your help!

EDIT: I found a solution to my issue. I just made myself a watercolor-ish background, and then used the Forever: Change Color Effect by (pick random 0.1 to 0.5)! It looks extremely good!

untitled script pic
Try using this.

Yeah, that's what I'm using, but I'm more after the distinct shape of each of the segments.

AFAIK it's not possible to do something like that, unless you map over the pixels in the stage such that only the background changes color. Maybe if all foreground objects were one color and the background didn't contain that color you could map over all pixels that aren't that color such that they change their hue.