End the end they turn red and become sweeter, 100% dark is also acceptable but when saving seeds I let them go red. For most things except pictures I actually let them go red
Cool. for regular jalapeños I definitely prefer red. I'll probably just wait to plucks these then until they get a little red. I pulled one early just to taste it, and it must have been way to soon, because it didn't really have any flavor yet.
Agree with Chris, they are nice and sweet when they get red. My plant threw out a lot of pods last year, but they were smaller than regular jalapenos. I am growing them again.