How to stop Submit button from being white and hidden until you hover the mouse

I am getting annoyed by this.

I don’t want the Submit button to be white and when I hover the mouse over the button, it will turn blue. I want it to be blue in the first place. Where do I modify this?

https://csd.dev.csd.org/stay-connected-csd/

I seem can’t access to main.css. Need to fix ASAP.