You can do this one of two ways actually. The first option is to adjust the "style vars" in your admin control panel. The second is to place the code below in your additional.css template. Either way the results are the same.
ACP -> Style & Templates -> Style Manager -> your style here -> Style Variable Editor -> Secondary Content
To change the TEXT COLOR you want to edit secondarycontent_color
To change the BACKGROUND COLOR you want to edit secondartycontent_background
To change the FONT you want to edit secondarycontent_font
To make the changes via the additional.css file
ACP -> Styles & Templates -> Style Manager -> your style here -> Edit Templates -> CSS Templates -> additional.css