Set Color and Opacity affects children of the button only, not the button itself. If you want to change the button itself, look into styles (Normal, Hovered, Pressed… and so on):
For each button style there is Tint which controls button colour separately. Btw, this is not something you want to do in Tick. Why not use FlipFlop when you press the button.
There is some inconsistency in the naming convention here; for other widgets this option reads Content Color and Opacity hence the confusion. It reflects the functionality much better. The tooltip is correct, though.