Consider that the new bride and groom are setting up house for the first time and they may not have talked about favorite colors that much. Likely everything in their bathroom and bedroom is a neutral color so far. I am thinking they just do not want anything so special to clash with what they might already have. No doubt you could do the beige and gray together effectively, but add a touch of sparkle in a tiny block somewhere. I'd be willing to say you and they would like it.