Customizing colors of data entry forms for credit card fields

I have a developer working on customizing the look of the WooSquare checkout plugin page and he is having trouble changing the color of the background in the boxes for filling in the customer credit card numbers. the site uses a dark gray background and the default form for data entry for the card info is black text on dark gray fields…this makes it VERY difficult to see your entered data as a customer.

I simply want to be able to change the background in these form boxes to white with black text. If we cannot do that, I want to use white text for anything entered on the black background.

He has tried, but cannot figure it out. Site relies on a lot of custom CSS for styling, but this form is not hosted on the site.

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