Oh, this is a great question! I'm ghostly-white, but every year I seem to get trucker's tan (tan only on my left arm from driving), which is even less attractive that farmer's tan. Because I am terrified of the sun, and because I am so pale, I'm not one for tanning beds or sun-worshiping in general.
That said, I would deal with overly obvious tan lines in one of three ways:
- Spray-on tan. A lot of tanning salons now have spray-on tan booths like Mystic Tan. The spray-on approach provides an even, all-over, natural color without the harmful, cancer causing UV rays you get from the sun or tanning beds. The tanning agents in the spray-ons work with your skin to continue to darken the skin several hours after the tanning session. Since the booths are private, you can get an all-over tan quickly and effectively. Plus spray-on tans won't wipe off or streak, which is a huge plus.
- Tan in a bottle. Self-tanners have been on the market for ages, and their formulas and application have become so much better. To help with a farmer's tan, you may want to blend in a self-tanning lotion into your whiter areas, working it in to the tanner parts of your skin. There are a lot of different formulas out there--ones that provide an instant tan, and others that continually darken the skin with continual application--so you'll have to decide what's best for you and how much time you're willing to deal with applying the lotion.
- Bare it all. Since you can't wear long sleeves, how about a tank top? That way your upper arms will be exposed and you'll have a more even look without having to work too hard. Changing what you wear may be all you need to do to combat the dreaded farmer's tan.