willard3 said:This is a common question.
You can use them either green or red.
Green go in salsa verde, in poppers and etc.
Red are sweeter and more picante and are used in salsa rojo, for chipotle and etc.
POTAWIE said:They will still ripen after being picked. Try the paper bag ripening method. Put your under-ripe peppers in a bag with a ripening banana or tomato and the ethylene gases will speed up ripening.