Can you post some pictures? To me, the Olympic Terrazzo Tan appears like it would read very dark peachy with grey and that may not be such a good thing. But it is hard to tell without pictures.

Aqua is striking with gray. A pale orange is a classic look too. You could also try a lavender or deep purple (if you have enough natural light or as an accent color on a wall with less space to be painted). We used BM's purple rain near a black and gray floor and it look great together. We have high ceilings, lots of windows and skylights, so the dark color is not closing in anything.
If you went with a washed out yellow, that is very pretty with gray... Basically, anything other than earth tones will work, although the burgundy/gray, mauve/gray and red/gray combos got worked pretty hard in the 80's-90's, so I'd skip those personally....

a strong yellow? mustard? turquoise? raspberry? celery green backed up by a spectrum of other greens? cherry red or tomato red? charcoal black? real coral?

Try a slightly mustardy yellow like BM Hubbard Squash or Tiger's Eye. Looks fabulous with the gray, as long as the gray isn't a very blue-gray. Post a photo and I'm sure folks will have lots of ideas for you.