Keep in mind that the continuous range of colors is divided up differently in different languages, and some of the colors the GPs know from their native languages may not have names in the language they are now learning.
"Where is the red paper? where is the blue paper? ..."
Materials to gather
Construction paper cut into small pieces and large pieces (and perhaps middle-sized pieces). Other objects that come in colored sets. These include candies such as Skittles. Colored pencils, sets of small toy cars, paper clips, tacks.