Changing background color and I forgot how I embeded Gallery.

I am trying to revise my wife's website: susanbanghart.com.
I can't remember how I incorporated Gallery 1.5 into the website. It was something I read on this forum and can't find.

Here is one of her pages with the Gallery in it.
http://susanbanghart.com/Gallery/Pastels

I want to change the background colors from black to a yellowish color. I know what my hex code for the color, I am just trying to figure out where to change it. Do I go into the skin css (I used the black skin) and simply change the codes or is there somewhere else I need to go?

Also in IE 6.0 or Google Chrome the site looks fine but in Firefox the images go to the bottom of the page.