The code I gave you makes an image for every chain of a structure. Here is a version of the code chain_images2.py defining the chainimages command that allows you to specify the chains you want images for
chainimages #1/A,B,C
I added that code the the ChimeraX Recipes page
For the coloring part, you could try to add that or you could simply color the structure before hand:
color #1 blue
color #1/A pink
color #1/B gold
Tom