http://www.scientificamerican.com/article/why-johnny-name-colors/

I thought this article was really interesting. It points out that even four and five year olds, who can do complex tasks like ride bikes, read books, and tie their shoes, still inexplicably mix up their colors sometimes. It explains why colors are so difficult to learn and references a study that found a way to increase toddlers' ability to identify colors.

The gist is that the English language puts the color before the noun around 70% of the time ("The red ball") which is confusing to their brains and almost makes them think the color is part of the object's name, whereas postnominal phrases ("The ball is red") help the child narrow their focus to the object and then recognize the color as a descriptor.

According to the findings of the study, your toddler will have an easier time learning their colors if you make it a habit to put the object before the color when pointing things out.

Do you see the bird? That bird is blue!
These carrots are orange.
Mama's shirt is red.

We're going to give it a try.