Color in Widget Header

Hello guys and ladies

Could someone please help me to change the color of the widget titles?
Below is a screen-shot. You will see that "Time till next event" and "Points standings" is very dark.
I need to make them a bright blue to white if possible.
I would be grateful for some help.
Thanking you
Kevin



http://www.shadowracingrsa.net/

Code:

.introduction .h3, .module .h3, .postbody .h3 {
    color: YOUR COLOR;
}

Thank you.
Where do I put this?

CSS stylesheet

I know this sounds stupid, but I can't find the stylesheet

EDIT: Found it!!
Thank you so much.

AP > Display > Colors & Pictures > Colors
CSS Stylesheet Yab