Ghost peppers become a bright, rich red color when fully ripe. The peppers start out green over their first few weeks on the plant. After growing for about 4 weeks, the peppers will begin to show shades of orange and shift over to being bright red after two more weeks.
If the peppers are left on the plant for too long, they will begin to show some black spotting at the top or bottom. The stems will typically dry up at this point and the peppers will continue showing a shade darker once they've fallen from the plant.