Cannot style active tab heading text

No matter what CSS I try, I cannot change the active tab heading from colour white. See on my staging site, test.rmrg.org.uk, accordion is at bottom of home page in left column.

Plugin settings are:
Default background color - #dfe3a2
Active background color. - #eaedc3
Accordions header font color. - #003310
Accordions header font color on hover. - #92977e

How can I set the active tab heading colour to what I want please?

Thanks!