Color is beautiful.  Kids remember more when they see it in color.  Using color paper is worth the extra $2.00 you might spend on a case of color paper.  The intensity level of the black letters on white paper is no more when you use color paper.  Are you having the kids write a nature poem?  Have them write it on a green sheet of paper.   Have you ever asked your students to pull out a handout from two lessons ago and it seems to take them forever to find it in their folders?  Try saying this, "Take out the yellow sheet of paper I gave you two days ago."  It's magic.