どんないろがすき？”What color do you like?” is one of my daughter’s favorite songs to sing, and it is a great one for teaching colors. The lyrics can be found here, and here is a video:
Another good video can be seen here.
Here are some printable flashcards for learning the colors, courtesy of 知育あそび＆子育てわあるど, a great website full of activities for the preschooler. You could also use these fruit flashcards to teach colors. I also recommend watching this cute animated movie where cartoon crayons teach colors.
Speaking of coloring… I just found the CUTEST website that has a bunch of free coloring pages for our little ones. The website is called 青色超人 … just go visit, you will love it!