Change Submit Button Text or Background Color

I’ve seen a couple of other posts on the topic but can’t get this to work for me.

The background on the page is black. The text for the Submit button is not showing b/c it’s white,which matches the button background. I had previously changed the font color of the form to white due to the background, which changed the Submit button text also.

I would settle for knowing how to change ONLY the Submit button font color OR the Submit button background color. Can anyone lend a hand?