I guess this depends on the TV in question!.
On the PS3 set RBG full if the TV supports it. I recently read somewhere that this makes no difference unless the TV supports it. I dont know more than that unfortunately except that mine appears to!

. I also have that super white thing on, but again I dont know if that makes any difference, it just makes me feel better! lol.
Its also worth going through the TV's display settings to see what options you have. For example, I find switching between display modes such as Normal, Dynamic or Cinema shows big differences, but its upto you as to which you feel looks better. For me my Dynamic setting works best as it seems to bring out the colours more and deepen the blacks.