Studio font - can't find where to change colour!

Hi there, I'm using the Studio theme (although this can probably be answered by anyone with some CSS knowledge).

There's a font that appears as the description for groups & as the latest update at the top of a member's profile - this font is in a light grey colour and several members have told me it's quite hard to read.

The trouble is that there doesn't appear to be anywhere to change this particular font colour in the Studio theme options (I've looked and tested believe me!)

Could anyone recommend a CSS tweak to the custom.css file that would fix this and make it black text?