I use F/O rear and .100 front that I make on all my iron sight revos. I use orange front and green for the rear. I find the orange is much brighter than the red.

When using F/O on both, the temptation is to just get the dots lined up somewhat close and break the shot. That does not end well past 10 yards. I find you still need to line up the notch and post the same as you would without dots to make an accurate shot. Where the dots really help is on the draw, between shots, and in low light conditions or dark background. The dots help keep track of where the sights are in relation to each other very quickly, then you can refine the sight picture all in one fluid part of a second. In bright sunlight (ideal conditions) I can see all black sights sort of OK, but in overcast, shadow of a tree, etc., the fibers make all the difference.