Well, of the people I personally know that have seen the Gray(the GalGray is available on the other Civic trim lines as well), most everyone seems to like or love the Gray. I don't, however - it just looks like 'muddy gray' to me. That, plus the fact you're getting an ivory interior in the GalGray, led me to choose the MagPearl, with its blue upholstery / carpet (save for the cloth on the doors). My last Honda had Ivory interior, and I swore I'd not make that mistake with this car - it requires constant attention to keep clean, especially in seasonal climates.
The MP looks like a 'steel blue' or 'gunmetal' to me. As dark as it looks in the pictures - it's darker in person. However, in sunlight, it brightens up a bit, and you can see the metallic finish when you get closer (it's a metallic, not a pearl, ironically). Since I wanted the blue interior, it was between MP and Alabaster Silver - and the silver looked too washed out for me, compared to the 'Satin Silver Metallic' that my '01 Accord had. Not to mention that I think silver is a bit played out in cars (yes, it's popular, but it's been around forever and a day).
MP (along with the Opal Silver Blue) is also exclusive to the Hybrid, if that's important to you at all. Exclusivity
can mean problems with paint matching, if you ever need to have the car repaired - that's something to consider, as well. Right now, I can't even find a touch up pen in the color - only the brush-on stuff, through the dealer - and that's a mess to apply.
Unless you put a clear or conventional bra on your car, expect the paint to chip on the front end, as you put miles on the car - Late model Hondas are notorious for this. The MP is so dark, that if you get a chip, you'll likely not notice it, because it's so close to the primer color. GalGray would mask this to a lesser amount, and the other colors will show chips like no one's business.
One last thing about the Galaxy Gray - the exterior will probably hide dirt better than any of the other 4 hybrid colors. If you live in dusty areas or don't wash your car often - this might appeal to you.
I don't have pics of my car online, but there are others who do in the 'Share' section. However, it's the same thing as a brochure. You really have to see the car in person to decide for yourself, if the color is the most important decision (the way the cars are optioned out, color preference and Navi are all you have to worry about

This is harder with the MagPearl and the Opal Silver Blue, since those are 'hybrid only' colors, and they don't sit on the lots long (14 day avg dealer supply on the '06 Civic Hybrid; 45 days is 'normal')
Good luck in making your choice - let us know what you decide, and why, once you make your decision!