Font colors are usually attributes of the themes.
I'd first try not to mess around to much and hence install another theme and try what fits my needs.
If you want to go all geek mode and fiddle around you will find the themes under
There you will usually find a
gtk-3.0 folder, in which you will find all the files of the theme.
The files you are looking for are either
settings.ini respectively both of them.
If you are familiar with css, you'll have no problem configuring your style as you wish to.
The interesting part for you might look like this, depending on the theme designer:
/* default color scheme */
@define-color bg_color #ffffff;
@define-color fg_color #4c4c4c;
@define-color base_color #ffffff;
@define-color text_color #ff2525;
@define-color selected_bg_color #cce8ff;
@define-color selected_fg_color #262626;
@define-color tooltip_bg_color #ffffff;
@define-color tooltip_fg_color #4c4c4c;
@define-color progressbar_color #06B025;
As you can see, colors are defined for different parts of an application, so you might have to try and find out which one you need to be changed.
To use the theme on your unity desktop, you will have to install unity-tweak-tool. It's also very handy because you can swith back and forth between themes and directly view your changes, once you saved them on the theme css file.
As a little bonus, you might find this article about theming in Unity very interesting: