-select this tool (you may need to right click to find it)
- click the + button to "add your selection" you can change the brush size (it is at 3 on my screen) if you need to
-select the whole wheel
-go back to the options and select the - button. "subtract" the areas you don't want to be colored
-click this (you may need to click a circle icon that is black and white)
- check this box and play with the bars!
Should be it!