Sizes And Numbers For Things In Scratch
Canvas: 480x360 (-240 to 240 by -180 to 180)
Colors: 1 to 200
if you do change colors and do 200, nothing changes.
From the wikipedia this is what happens if you start with the original color for the orange cat and then apply the change
1-10 = Orange to light yellow 10-20 = Light yellow to a yellowish-green 20-30 = Yellowish-green to a medium green color 30-40 = Medium green to a thick, green color. 40-50 = No considerate change. 50-60 = A greenish-light cyan color. 60-70 = A lightly-blue tinted green to a fully light cyan color. 70-80 = A light cyan color to a light blue color. 80-90 = A light blue to a medium-dark blue. 90-100 = A medium-dark blue a thick dark blue. 100-110 = Darker and darker blue. 110-120 = A slowly more purplish-blue. 120-135 = Violet to Indigo 135-160 = A gradually mixed pink and purple. 160-170 = A gradually pinkish-red color. 170-180 = A thick red color. 180-190 = A dark orange color 190-200 = Identical to the original color at this point.
More details on the colors and graphic effect here: