Acceptance text color

Hi!

I have two different forms on different pages.
In my homepage floresnocais.pt I want my acceptance text to be black because the background is white. In other pages like floresnocais.pt/avencas I want the text to be white because the background is dark.

I’ve created a CSS class in one of the forms so I can change the colour but it’s not working. I don’t know what am I doing wrong. Can someone help me with this?
I’m founding it tricky and I’m not a CSS expert… :/

The page I need help with: [log in to see the link]