I don't know how other people do it, but with my five kids I have found this method to work when teaching young ones their colors. I like to point out different objects of the same color (this works great on a walk-- I like the color red to start with, because there are things like fire hydrants and stop signs), or similar objects of different colors. I have used these blocks to teach each one of my kids, because it fits the similar object theory, and we can organize the blocks according to color. With my others, I started shortly after their first birthday and expect that the colors and concept won't click completely for six months or so. I know this feels like a young time to start, but in some ways it reduces pressure because you know there is plenty of time, and they really are sponges at this age.
I don't know how many times I had to make a concerted effort to sit down and work with them on colors, but I'm sure it took less than ten. Once they get it, it is pretty easy for them.
I waited longer than usual with my last little boy. Today we finally got to spend a little more quality time together than we have over the last couple of weeks as we had no doctors to visit or places to be (by the way, our little girl is doing well! she got a "clean" X-ray yesterday and her blood markers are showing back to normal! Wahoo!). I'm not sure the color part sunk in, but he loved the tower building and matching up the colored cars to the different colored towers. I forgot how therapeutic it can be to play cars with little ones. So fun.
How do you teach your kids their colors?