Good tool is your browser. Firefox (I use Mac but probably same for PC) has add-on called Firebug that allows viewing code elements. So if you need to know what the selector is for the title, it will show <h1 class="foo"> for example.
The Theme is set for each album under the Themes tag, of course. Then go to Options tab and select Theme Options. Select each album from the drop down menu and scroll down unti you see choice of the css options. (Keep forgetting to ask if it could be moved up on the page
Within the Default theme is a folder /styles. ZP's css files are there. Clone whichever you wish and give it a name. Go to the Admin panel and it'll show up as one of the selections (make sure the page was refreshed.)
I use my FTP application to view the css file live and modify on the fly editing with BBEdit. An HTML/CSS editor is, IMHO, extremely better than plain text editor. Every time I change it and save, I refresh the screen showing the php page to reflect changes.
Take your time. Record your changes as you go to reflect what it modifies. So, if you change #FFFFFF for the gallery title to #000000, add /* this changes the gallery title */. That way, when you want to create the next css for Album2, you know what to modify. And, make sure your css is valid, of course.