Pthalo blue is always on my teaching supply list. Most educators shy away from this color because of its intensity. It is a transparent blue which means it’s a wonderful mixing color. Most painters use it for mixing as it will almost look neon by itself and is an unrealistic color. But, mixing it with other blues gives depth to the color. Mixing it with cadmium yellow makes a fab grass green. It will stain your clothes and the palette – not everyone’s idea of fun. But give it a try.