I found these white containers at the dollar tree and they fit notecards perfectly, so they are great for this color sorting task. I took a bunch of blank notecards and drew different designs on them using blue and red. I used a variety of blues and reds (crayons and markers) so that the student would be working on generalizing what "blue" means from the get go and not only associating "blue" with one specific color.
At first, my student was just responsible for sorting the cards into the two containers. Now that he has that mastered, I hold the deck of cards and make him say the color "red" or "blue" before he can take the card and sort it.
I also use this fluency timing with him. I set my timer for 30 seconds and he goes through the colors and tries to say each one. We count how many he got and keep data on the bottom of the page for each day of the week. For a packet of these fluency timings (covering a variety of other topics as well), check out my TPT store.
He is doing great with this! Soon, I think he will be ready to add in another color! Next up....GREEN! Happy Friday and have a great weekend!