RE: How many pins do you prefer??
I've always used three for my Midwest whitetail hunting: 20, 30 and 40... Green for 20 (you've got the green light; let 'er rip!!) Yellow for 30 (Are you sure you're not gonna get a better shot? If not, go for it!) and red for 40 (Stop! Let's weigh your options here... Be sure of everything...)
I've added a fourth for 50 this summer in preparation for my upcoming elk hunt in Colorado... went with green since it was the furthest color away.