Why can I not find the right CSS? - Color Change

[southshorepizza]

I cannot find the right place to change the black text header for boxes. For example on the logon page.
"Returning Customers: Please Log In"
"New? Please Provide Your Billing Information"
"Company Details"
"Billing Address"
"Additional Contact Details"
"Login Details"
"Newsletter and Email Details" and so it goes all the way through the checkout. I have managed to change mostly everything else I would like. However I can't seem to find these. Perhaps they are not defined? If not how could I easily define them. It happens all the way through the checkout process.
http://onlineorder.sshorepizza.com is the website if you want to see what I mean.

Also in the shopping cart area the text inside that box is currently yellow on white. Which is hard to see. I can't seem to find that setting either.

Thanks in advance for your help.