Color relationships are an interesting thing to try to teach students who are color blind, or completely blind. We've been reading the picture book about Esref Amarmagan, the blind artist from Turkey, who had to keep his colored pencils laid out int he same order, and memorized the color of objects, so he could recreate them in paint in a way that made sense to future viewers.
When I asked one class,"What color is a watermelon?" A couple girls, with some vision, answered, "Green!" But when I followed up by asking about the color of the inside of a watermelon, a boy, with no vision, eagerly said, "Green!" The only way for kids like him to know the colors of things is to be told.
So we talked about the color of things, and then we worked collaboratively to make a giant collage of hundreds of 1 inch squares of color. First, I used Elmer's glue to trace the giant chart paper grid. After it dried, students felt the squares and were able to independently glue and place their pre-cut 1" squares or origami paper.
Each child also made his/her own, "Homage to 'Homage to the Square'" piece gluing various colored squares together and trying to explain why they thought their combination was working.
Extra time meant gridding another giant piece of graph paper with glue and having students use dot makers to make color clusters and patterns. What a corful way to start the school year!