All a matter of opinion. Depends on how you are gonna cook em, pickle em, freeze em, use for salsa, smoke em, dry em, poppers, stuffed peppers, etc.

Ask a dozen people u may get a dozen different answers.

Personally i like my Serrano's and Jalapeno's green, and my Cayenne's red. Dont have much experience with those other pepper types.

Jim

I just enjoyed my first red Serrano yesterday (in egg salad).
Really nice flavor, a little sweeter and nuttier with a slight increase in heat. My red biker Billy Jalapenos are scorching hot.

I actually wrote a post on the PEPPERMEISTER blog about this very topic.

Here is a link that might be useful: Here's my recent post about the Red or Green debate.

thanks for the link, peppermeister! nice!

I let most ripen. Some that I use green are Serrano, Big Jim, and Poblanos. But, even those, I let ripen depending on use.

Call me old fashioned, but I like to let 'em ripen.
I also like the look of the colorful pods on the plants all at one time.
Of course, around here, that doesn't happen until September.

As Tsheets mentioned, I, too, have used Poblanos in green form (same with Pepperoncini).
I think I prefer them ripe, though.

Even Thai chiles, which are often sold/used green, I prefer ripe.

Josh