Where do I go to edit this?

It’s in your stylesheet, called “blockquote”. Look for this line:

.SCS blockquote { padding: 2px 10px; background: #e9f8ff; margin: 0px; color:#336699; }

You have a couple different blockquote styles depending on where it’s placed in your page so you might have to try changing different ones, but if you want to change the background color just replace the color:#336699; with the hex for whatever color you want.

thanks!

Where do I edit the colour of the text within that box?

In the very same estylesheet:
.SCS blockquote { padding: 2px 10px; background: #e9f8ff; margin: 0px; color: #336699; }

background: #e9f8ff; —> background color
color: #336699; —> text color