Buy a pair of binoculars from the dollar store. If you don't want to buy a pair, you can make a pair using toilet paper tubes. After reviewing the primary colors, send the children, armed with their binoculars, on a hunt to look for colors around the room. Have them come back to you and report what they found.
Buy or make bean bags in all of the primary colors. Draw circles on a white poster board that corresponds with the colors of the bean bags. Hand the first child in line a bean bag and ask her what color it is. Then let her try to throw the bean bag onto the matching circles. Another idea is to have children tell you what color bean bag they are holding and then throw it though a hula hoop you are holding out.
Make two matching sets of color flashcards. Before the children arrive, hide one set of flashcards all over the room. Then review the names of the colors with the students. Give each child one flashcard and have them try to find the hidden one that matches it. If they find a flashcard that someone else is seeking, they should leave it there and keep looking for theirs.
Preschoolers love to sort things. Put different color construction paper circles at the bottom of cupcake cups. Let children sort colored objects into the different cups. Some items that work well for sorting are M & M candies, jelly beans, pom poms, buttons, colored popcorn kernels or even a colored cereal like Fruit Loops.