I'm not on my Win 7 system at the moment but I'm fairly sure it's the same as Vista.

Right click any part of the Desktop and select Properties. In the window that displays, select "Windows Color and Appearance" The display in the window changes and at the bottom is an option to "Open classic appearance properties for more color options". Click that.

A smaller diaog window will open. Click the "Advanced" button. In the new window you can select Windows elements, eg Active Title bar, etc under the "Item" option, then change the font size, color and type below.

Beware, make sure you know what they were before making changes. It is easy to 'get lost' here with multiple changes and you can end up with a horrible looking display.

I hope that helps.