Yesterday I scanned some comics I drew and I wanted to color them the way they appear in the newspaper, to give a sense of actuality to it. You know, the pattern of dots that gives white places a sense of a shade of gray (I assume by tricking the eye). It took a while, but I finally found the shade of gray I wanted to change actual gray to those dots in Photoshop. So I colored it gray, then went to Image > Mode and then changed the number of available colors to 2 under "Indexed color". I changed the palette from "exact" to "Local (perceptual)" and changed the dither to "pattern". The shade of gray needed is #808080. I tried tons of things, like #888888, but it wasn't exact enough for my liking.
I looked at the color in "set foreground color." Red, green and blue were exactly at 128 which is where I wanted them. Setting it at #888888 had that number at 136. Which I find odd, since you'd think setting them at all 8s would make it the middle color. I guess I'm kinda stupid.