On one page, ESL teachers can show (with an interactive board) the colours to their students. Key elements as colours can be useful and this poster can assist student during their activity.
I never know as an ESL teacher if I'll have my classroom or not. When I don't, I like to ''travel light''. Going from one classroom to another with many posters, a cart and other things can complicate our job. I hope this will simplify it!
Have a look at the Shapes Poster!