Is a black patch on an unripe pepper a bad sign?

A dark purple or black area can be pigment or a response to strong sun, so color by itself doesn’t prove the pepper has spoiled. Some peppers also change color as they ripen. Check whether the patch is firm and dry rather than assuming it’s unsafe from appearance alone.

Give it a close look and feel. If the spot is soft, wet, sunken, spreading, moldy, or smells off, discard the pepper. If the rest is firm and normal, you can cut into it and inspect inside; remove any damaged part, and toss it if the flesh looks spoiled too.