The fruits of pepper plants such as sweet bell pepper (Capiscum annuum) come in an assortment of colors, but the colors are just indications of just how ripe the fruits were once they have been picked. A red bell pepper fruit is from the exact same plant species as a green bell pepper fruit, only picked later in the season. Once you cut peppers off plants, then they will not continue to ripen — generally.
Usually No Post-Harvest Color Changes
Sweet peppers usually do not continue to ripen and change color once they’ve been picked. If you pick them if they are green, then typically they’ll stay green. If you would like peppers that are yellow, yellow, red or brownish, then abandon them around the plants and keep checking them to see if they have reached the shade you want.
The 1 Exception
1 scenario where peppers continue to change colors after their crop is noted on the Bonnie Plants website, but the conditions are very specific: They have to be harvested in fall during relatively cool temperatures, and they have to have only begun to change color. If you keep them in a warm, indoor room — Bonnie Plants does not specify a fever — you could see color changes for up to three days. That period, however, may not be long enough to make peppers turn red.