Fair warning: mojoPortal skinning is almost 100% CSS-based, so if you don't think you can learn it, or don't have interest in doing so, I'd recommend that you either hire a professional to do your skin or perhaps buy Artisteer. Even with Artisteer you'll likely still have at least a little CSS tweaking to do though.
If you do want to learn CSS, I'd highly recommend that you get the Firebug plugin for your browser, and use that to explore how the CSS styles the different areas of a skin. I knew the fundamentals of CSS coming into mojoPortal, but once I started working with Firebug everything became much more clear. When you see how the CSS selectors work, and their hierarchy, you'll be able to better understand the documentation here, and Firebug will help you pinpoint what CSS needs to be changed in order to set your new color.
Jamie