I'd like to first say how wise you are in tapping the breaks to carfully consider which gray to use. Majority of people think any gray will play well with any color but nothing is farther from the truth. So called neutral colors can unbalance an otherwise good set of color combos. Neutrals such as beige,white and gray appear to be without color but they usually have undertones of red,yellow or blue and in some cases,a hue from one of those families. You need a color consultant,preferablly from BM where you bought paint for this job. If the store doesn't have one on staff,ask them to steer you to one repersenting BM. If they give you the deer in headlights stare,call BM direct or go to SW where they will cross referance the colors. They will look at each color already used to determine how much of how many hues you have then decide if you should A. Introduce another hue(color) with the gray undertone B. choose a gray with undertone matching an existing hue(color). Where there's not a lot of sq ft area, textures,fabrics and such,3 is about the color family limit. All this information can be determined by looking at formula for each paint used. What they need from you is value (darkness) of gray you like. There's an industry standard for gray value of 1 (almost black) to 10 (almost white). I hope that isn't confusing you farthar but a consultant will understand and do all the heavy lifting for you. I would expect BM to do this free of charge considering the amount of paint already purchased. If cost or lack of cooperation leave's you talking to yourself,contact an artist friend or artist's supply store. They deal with this every day.