Depends what you're going for. If you want a green jalapeno then pick it when it turns dark green. Or if you want it red, then just keep it on the plant til it turns a dark red. Habanero can be picked green but I think most people prefer the orangish yellow so wait until theres no green or paleness to the color. If you're planning to harvest seeds from them, you want them to stay ripe on the plant for as long as possible.