I’d like to change the color of the buttons and lower the point size of the legalize copy. I tried changing the <p> on the master CSS but it changes it for the entire site. Could someone point me in the right direction?
First, you want to be careful about changing global css:
p, li, a, etc.
because no matter where you put it, it will apply to any element on the page. You should scope your css.
The yellow button doesn't work, but there is a link labeled "click to open" at the bottom of your page. That opens a popup. The popup's most outer wrapper has an ID you can scope off of like so:
#bbs-modal-window p {
/* some css */
}
and this will target the paragraphs specifically inside the popup.
In an effort to keep things modular, I would suggest finding the custom module containing the popup, and changing/adding css to the css area of that specific module. You should still scope your css as described above.