I am trying to create graphics that I can later use in my web application. I want my web application users to be able to customize the colors, and I was wondering if there is a good way to do this. For example, I want to have a picture of a person's face with black hair and black eyebrows. I would like it if these colors were some how "variables" so that the user could change the hair to blonde and the eyebrows to brown (for example).

Is this possible?

I see in the description for Adobe Illustrator (http://www.adobe.com/svg/tools.html) that it has this feature:

Turn any piece of artwork into a template for data-driven graphics using the Variables palette

This sounds like exactly what I need. Can InkScape do the same?

I don't believe so. I'm not familiar with using Javascript with SVG, but I assume someone already familiar with JS will not have too much trouble doing what you want without the aid of software like Illustrator.

View the source of http://tavmjong.free.fr/INKSCAPE/DRAWINGS/clock2.svg to see how javascript is used to animate the clock parts.