Change color and size of font for 'Name', 'Subject' etc

hi there,

We are looking to use your plugin to make a contact form on a site that has a black background – see this screenshot

http://lexbridgelawyers.com/wp-content/uploads/2014/11/Screen-Shot-2014-11-16-at-12.58.53.png

How can we easily change the font color and size, so that these can be read against the black background, and also the form fill color?

I tried adding in some changes to the contact-form-with-captcha/cfwc.css but these didn’t work or impacted other elements on the site.

Any suggestions of an easy way to change these details?

Thanks

https://wordpress.org/plugins/contact-form-with-captcha/