Grey looks grey on my device. I've compared it to about 20 different devices I own (all with different display types) and I haven't noticed any different beyond greys being a tad darker on AMOLEDs, which isn't surprising.
The only time I found there to be an exception was when I set the brightness to 25% or less and held it up to my (far brighter) LED TV. There's an extremely subtle yellowish tint to it that I only see in this case. Immediately moving it away from my TV it looks perfectly fine again.
Long story short: You should be ok, and I wouldn't consider it a reason to not pick up the phone. Even if it were an issue, the device's pros far outweigh that minor detail. Plus you'd likely get used to it over time. Personally I think the screen looks incredible, better than on most other devices I've used.