As Robert said using images would make no difference.
On my PC with new Samsung monitor and optimal settings I can still barely see #f2f2f2 while on the Mac its as bright as a (bright) button. You just have to design with this in mind and user more contrast if its an issue.
One of my clients complained that when he turned his flat screen monitor at a large angle away from him the colours looked different and could I make sure it doesn't happen again!
I came up with a solution but it involved nailing the client and the monitor into a fixed position which wasn't acceptable