Member css

Question..

I copied the member.css file to the child theme (inc/css)". I want to make an color change to the "create a group" button. The color change edit is not registering.

Can you help?

Related question.I am somewhat new to making these edits. Is it a big drain on resources to copy over the whole folder...or do I just want to edit that button in the member.css.

Thanks

John