I grew these up in northern Illinois and they were fantastic low-effort plants that pumped out buckets of peppers right alongside my tomatoes. Green is classic for these Hatch-style peppers, but the red color is beautiful and makes for a wonderful red salsa when combined with red habaneros and black poblanos.
You can pick them when they're green, of course, they turn red after getting to full size so I only let a portion of them get fully mature and change color. Hard to go wrong with any of the Joe Parker varieties, but this one was a fantastic multipurpose pepper.