To get color by numbers, type a, b, or c. Click on colored circle to select color; click again to deselect. Click on number that coordinates with selected circle to color.
You will have to click the circled color multiple times during one color. For example, if I clicked the red circle and then click the one after I will have to click the red circle again before clicking another one. If you click the squares fast you might be able to get two or three without clicking the circle.