Anyway, some shoes certainly are lower-key than others. Montrail's Vitesse II ($85; www.montrail.com) are strictly business. Think non-flashy blue and gray uppers, and useful features such as a Phylon midsole (a little stiffer and more durable than EVA) and grippy outsoles. New Balance's 976 runners ($99; www.newbalance.com) don't even look like a trail-runner, and in fact they're billed as a "country walker." But their tough sole and well-placed cushioning make them perfectly appropriate for running on trails, and their brown leather uppers won't even look that out of place in the office. Lastly, I think Salomon's XA Comp 2 XCRs have a look that says "serious about trail running" but not one that's too over-the-top. They're $100 (www.salomonoutdoor.com), have uppers of synthetic leather and mesh, and have Gore-Tex liners to keep your feet dry.
In any event, a light coating of mud and dust will help your shoes blend in to the environment, so maybe a little color out of the box isn't a bad thing.
For a look at more trail-runners oozing form and function, check out Outside Online's Trail Runners Buying Guide.