chillies

A lot depends on the variety but if what you have is hot peppers of some variety, you can pick them at just about any point, I pick Jalapenos just as they turn dark green but I leave Cayennes until they turn bright red. This is not to say you cannot do exactly the opposite if you wish. Some varieties have very little color change and so I just pick them when they don't seem to be getting any bigger. If you are planning on drying these chilis you should let them get completely ripe, which is red or orange for most varieties.
Hope this helps you some.

I would agree with Wohlibuli..BTW the more you pick the more new flowers grow