To review a color with your toddler, you might try a color scavenger hunt collage. Spread some things around the house for the child or children to find that are the color you are working on. Your scavenging hunter/s will turn their finds into a collage with which to remember their hunt.
Ideas for items that can generally work for any color include, craft pom poms, feathers, colored Popsicle sticks, colored pasta, buttons, stickers, large sequins or bits of confetti, paper strips and scraps of paper, yarn, tissue or fabric. If you have time, you might try printing some small pictures of things you've found ahead online and cut the pictures apart so that each picture is no bigger than 3x3 inches. Pictures of common foods or items that are often associated with the color in question are particularly nice. For example, a stop sign, cherries and apples for red or a banana and egg (showing its yolk) for yellow.
If you have a tiny one in the house that might still put items in his or her mouth, you could do an old magazine scavenger hunt and allow your older child to look for the color in the pages of an old magazine to create their scavenger hunt collage instead. The advantage to this one is he will also get practice with cutting skills while she is at it.