Creating natural looking color at home can be tricky, but with a little planning you can achieve great results. If you can't go to a salon and have your gray professionally covered, there are some fairly good supermarket brands on the market. You'll want to choose a semi-permanent color which will fade after a few weeks of regular washes (Clairol Natural Instincts for Men and Just For Men work well). This will prevent you from having to touch up the roots on a regular basis. When choosing a color, you'll want to go a shade lighter than your natural color. Remember, you don't want a new color, you just want to get rid of the gray you have. To keep your hair looking natural, you should simply tone down the gray, not totally obliterate it. Choosing a color one shade lighter will help achieve this goal. If you choose a color darker than your natural hair color, the results will be highly noticeable -- not the subtle look we're after.
Here are few more tips that will help: First, read and follow the instructions exactly. If the product says to leave it on for 20 minutes, leave it on for 20 minutes. And, yeah, you really need to do that "patch test" thingy. When coloring, you can help avoid staining the skin by rubbing a bit of Vaseline around the hairline to prevent the skin from soaking up the color. If you do get some staining, rubbing the skin gently with a bit of Sea Breeze toner should do the trick.
At the Salon:
These days, there are several quick and fairly inexpensive options available to men in the salon. My favorite is Redken for Men Color Camo -- the service only takes 10 to 15 minutes and should cost you around $25. American Crew's Precision Blend is another excellent quick color service that will blend away gray and take years off your appearance while still looking natural. Both options last about six weeks and fade without brassiness.
For most men, I still argue that working with your natural hair is the best option. A well executed haircut and fit, healthy body will do more to keep you looking young than covering the grey - think Anderson Cooper. If you really want to reduce your grey, the best option would be to seek the talents of a professional hairstylist. If you do color at home, make sure to follow the instructions and use the tips above to get the most natural result possible.