The main tabs on the Super User homepage use two different colours for the borders:
On Stack Overflow, a single border colour is used:
Similarly, on Meta Super User it looks like:
Is the different colour scheme for Super User (and for Server Fault) intentional? If so, why?
For convenience, here's how the current, all #CCCCCC and all #999999 schemes would compare. I think the "all #CCCCCC" version looks more consistent.
.subheaderstyles differ between sites and the color for#tabs a.youareheredon't.