In a book!

You can read your child a story point out the color of the week when you see it.  Encourage your child to also point out the color as you read.

Draw a picture using only that color

When focusing on one color, you can have your child draw a picture of anything, but only give him a crayon in that color.  The picture will still be fun and you get to talk about that color the whole time!

You could also do this activity with the color you are currently learning and all the past colors that the child has learned.  Then, as you color, talk about each color the child is using.  Let him decide which color to color with because then he will enjoy it more.

Looking for Colors Around the House

I did the same activity that I blogged under Shapes (Looking Around the House) but did it with colors.  The color of the week was pink, so we walked through out the house pointed out all the things that were pink--a lot more now that we have a baby girl then before :)