All of my consoles (except for a 360 slim) are skinned with Decal Girl skins. They're the most trusted skin company I've come across. Most console sites that sell skins, get them from Decal Girl. Their products are top notch. If you don't want to skin, you
should check these out (my unskinned slim is in one)...
DecalGirl is positively reviewed at Resellerratings.com (www.resellerratings.com/.../DecalGirl). I wouldn't have any qualms about buying from them. You can Google for
"Xbox skins" and probably get a bunch of other options.
Microsoft does not have different color options as part of the base offering, though there are occasionally special versions (i.e. the Modern Warfare 3 special edition console).
I personally haven't used them but if you click on the link, it has "McAfee Secure" at the top and "Truste Secure" and a "BBB Accredited Business" and a few others at the bottom. But honestly, I don't know, other than what they say. Any online transaction
is iffy in my book.