We talked about several examples. If the story has the little girl wearing a pink dress, the illustrator can not say, "Nope, I like red." ...... and color the dress red. If the author has the boys in the story playing football, the illustrator can not say, "Nope, I like basketball better." ..... and color them playing basketball. Otherwise, he might loose his job. "You mean like get fired Mrs. Rucker?" Yep! The author gets to tell the story, and the illustrator makes it visually come alive.
One of the activities we do to practice this is play our "Be an Illustrator" game. I have the kids put up their desk dividers (so they can't see each others papers), and then I tell them to put on their Illustrator hats. They must listen to the sentence and illustrate what they hear. When everyone is finished coloring, we show our pictures. They love to see if their picture looks like the others at their table. The sentence I used in these pictures was, "The fat yellow cat sat on a blue mat." :)