My classroom is such that at any given time I could have numerous therapists in my room. The children in my classroom are very young and often multiply impaired and the earlier we intervene the better the outcome. The occupational therapist is great fun and always has wonderful interesting toys one of which is Changeables. Changeables are markers that change colors when a neutral marker is placed on top of a color and presto chang-o a new wonderful color appears. Well, that is exactly how DS color Nickel Azo Yellow reacts with Phthalo Green Yellow Shade. It's such a pleasure to see the dark green change to a beautiful yellow green before your eyes. Delicious.