Overall they look good, a few notes and answers to your questions.

• The outer shadows seem to be missing, you can see them on http://33cc77.com/wikipedia/

1. The colors. I took them from https://www.mediawiki.org/wiki/File:Guide_Color.png but blue looks kind of dim. Blue, green an red also don't seem to have the same level of perceived lightness. Is that OK?

I just checked the colors from Guide_Color.png and the button blue isn't there it should be #347BFF The other colors are spot on.

2. Quiet buttons. I remember clearly from talking to May that we wanted them to be colored in their default state and make them slightly darker in hover. I don't remember what they were supposed to look like when disabled. Right now they're slightly lighter but maybe they should be all gray?

Thats not quite right, unless May changes it the quite buttons should be black normally, their action color on hover, and the action color click state (darker version) on click. https://www.dropbox.com/s/amh0gfgc1p2i6c6/Screenshot%202014-01-03%2010.24.45.png except for the neutral state which is normal:black -> hover:#747474 -> click:black

All of the disabled quiet state buttons should have the same text color as the background color of the primary disable buttons which i'm pretty sure is #BFBFBF

 

3. Focus state. Right now it's the same as hover state, but I'm afraid it might not be enough for people with poor vision or color-blind who use keyboard for navigation. Opinions?

I think we should use the hover state for focus state (which is what you're doing) and suppress any browsers highlighting or borders (which is seems like you're also doing) So I think we're good to go there.

All in all, these look awesome, I can't wait to get them out in the world. 

 

Thanks,
--
Juliusz