Have you tried balloons? Blow them up and let them go. When the children catch them, what color do they have?
Pictures or sketches are good. Get two sets. Make a card game or a memory match with them.
For memory match put all the cards face down on a surface. The students turn two or three over and name the pictures as they turn the cards over. If they get a match, two identical pictures, they keep them. At the end the one with the most matches wins.
You are talking about an age group with a very short attention span. You have to be prepared to entertain them, but at that age, they will quickly join in and learn as they mimick what you do.
Good Luck.