How to customize the product page theme

My theme has ugly color combinations for the ADD TO CART / UPDATE CART buttons. It is green and the text on the page is gray or blue. I don’t have a lot of customization experience, and would like the button to be BLUE on White text like the rest of the theme.

How do I fix this. Seems like there are no good themes to work with this plug in other than the bland framemarket theme :disappointed: