Unripe serrano peppers are green, but the color varies at maturity; common colors for the ripe fruit are green, red, brown, orange, and yellow. Serrano peppers do better in soils with a pH between 7.0 and 8.5 in warm temperatures above  and have a low tolerance for frost.
Unripe serrano peppers are initially green but change color as they mature; common ripe colors include green, red, brown, orange, and yellow. Serrano peppers grow well in soils with a pH between 7.0 and 8.5 at temperatures above freezing and have limited tolerance for frost.