We have some templates where we need someone that can make color variations of them. You don't have to be an expert designer, though having a little eye for what looks good is helpful. You are not changing the layout, just the colors. It is all done in CSS and you need to produce a new CSS file.
Where you need some PHP knowledge (and a little smarty too), is in our admin panel there is a template selector, and you need to understand this, and make sure you can add these new variations so the admin user can select. We have somewhat a working model on this, but maybe not perfect, so PHP is definitely required.
This is for phpLD which we sell at phplinkdirectory.com and you can see exactly the CSS code you will be dealing with here: