iMovie doesn't support Graphite appearance?
I believe "that graphite look" you refer to is merely the color scheme that Apple uses for its "Pro" applications to distinguish them from its consumer level applications.

iMovie is a perfectly good (if limited in what it can do) application that can be used quite successfully to edit and finish up home or amateur video projects. If you need some features that iMovie does not offer you can switch to Final Cut Pro or Adobe Premier