the 'palette' at the right is constructed by interpolating between six images that are mostly a single color: red, orange, yellow, green, blue, indigo. when painting in the applet, the brush blends between two of these images based on the angle at which you're drawing. for example, if you paint directly upwards, you will get 100% of the red image, 60 degrees to the right, you will get the orange image. painting at 30 degrees will produce a blend between the red and orange images. applet by ben fry (email)