There are several different methods. Here are two of them...
1. If you use Pick Point Hatch, then after applying hatches, select the region whose color needs changing (by pressing Shift+S to turn off any Running Snaps and clicking inside the region). Then open the Pen Colors list (at the top of your screen by default) and click the desired color.
2. Before doing any hatch, change the Pen color used to outline the region (e.g., draw the outline of the tire in Black and the outline of the hub in Red). Then select one of these outlines, open the Brush Pattern list at the top of the screen, and click on "Solid." Repeat for the other outline(s). If you find that one of these hatches lies over another and hides it, select the offender, open the Format menu, and select "Send to back" or "Back one" -- whichever works.