The phrase "to color the pictures" means adding colors to a black and white drawing or to make something more interesting or exaggerated.
Sentences with «to color the pictures»
The BEST part about this book was the full page color pictures of the crafts and some pretty adorable child models. (naturemoms.com)
The upgraded paper and color pictures in the first half are very attractive and add a lot to the visual appeal and overall quality feel. (firstthings.com)
You can't combine that formatting with the double page spreads of color picture books as explained below. (indiekidsbooks.com)