Generally grey, but change to blue or green depending on clothing and mood. If I wear a lot of green, like my JROTC uniform when I was in high school, they'd go green, or if I'm extremely mad...not just annoyed, more like 'completely unable to control my rage' level mad, they tend to go green. Also went green on my wedding day and a few other very happy occasions, so apparently that gets it too.
Extremely sad occasions seem to draw out blue, as does dressing in a lot of blue. Otherwise...mixed clothing or just usual meh, and they stay grey.