A colour script defines the lighting and color palette used in Pixar's movies.
This needs to be done to keep the look and feel consistent.
A colour script takes those definitions and expands on them by providing a rendered or filled storyboard (or more accurately, frames from the storyboard) that show what the look is supposed to be like.
There’s a science to choosing colour schemes in a movie, to make the movie visually more attractive and provide psychological assists, and how designers use complementary pairs in a movie’s art design.