Zen 1.3.7 customized.

On the standard Zen product listing page, at the top, is the Filter Result By: form with both Manufacturers drop down box and the Alpha Filter drop down.

I'd like to re-style these forms with larger fonts and a coloured background.

Of course the template Stylesheet CSS covers the FORM styling but if I alter this all other Zen forms change too - including the login page.

How can I independently alter the 'Filter Results By:?