I like Black myself because you can get colours to pop, photos draw you in and black is a seducing colour. Grey is suppose to be easy on the eyes, but that's for photo editing. Certian fonts draw people in too.
If you're looking to appear very serious all the time (such as world news sites tend to do), go with the grey. If you want to appeal to readers on a bit more personal level, go with the blue - it brightens it up a little bit.
I've always said the more contrasty the better. I like black, because you can have fun with contrasted colors on top of it. The only thing that looks good on white backgrounds are really dark shades.
Beyond that, you need to think about audience. Blue is definitely a good feeling, grey and white have a more 'professional' appeal. I've not seen a green really work, but reds and pinks do if you have that kind of audience....