I've got a 450h in Mesa Red and I haven't seen another GS in that colour. When it's not sunny it looks like a nice burgundy/wine colour, when it's sunny it's a lovely cherry red - so you get two for one.
Used to have a dark Blue 300 a few years ago and that was very nice but a little common.
The really light colours don't suit a car that big - they look like bars of soap!