A single color collage is a great activity for young children, especially if they have expressed an interest in colors. My little guy is almost two and a half and he has been really into naming colors lately. There is nothing to this--just a bunch of blue "things" and some blue paint and glue. You can let your child decide what color to use. You could even go on a little treasure hunt to search for blue or yellow etc. items. I should mention that this particular project with my little guy lasted only about 10 minutes. I also sat with him and helped. Some little ones will spend more time, some less. I think it is important not to pressure them to spend more time. It has to be fun!