I couldn't care less what color the resident chooses to paint his apartment. Heck, he can paint it black if he wants to. While he's living there, keep the apartment clean, pay the rent on time, don't ask me to do you a favor I cannot grant to everyone, and decorate to your heart's content. When you move, as per the Lease, the unit must be returned to "move in condition." I don't want stains on the carpet, cigarette burns on anything and no smoking smell permeating throughout the apartment. I want holes patched appropriately and no other damage.
New Prospects used to say, "Really?????" I'd look at them and say, "Sure, it's your home." I found 80% of the residents resist the temptation to go too wild at move in and wait until they settle in for a year. After that, rarely will they go crazy re-doing the paint. In fact, they will say, it's not important because the walls aren't white when they move in (it's painted a pretty neutral.)
Now, for those residents who choose not to paint a color of their choosing, and they stay more than a year, the Benefits of becoming a long-term resident kicks in: we will re-paint your apartment after three years (if needed); we'll replace carpet after five years (and I'll let you pick out what you want within a few guidelines with my carpet supplier/installer). After only a year, we clean the carpet. After a couple of other years, we may change out a fixture or two or install a ceiling fan in the master bedroom. In other words, there is a Rewards Program. I believe in the power of making yourself at home.
Sandy, I suppose you could charge an increased security deposit for those who choose to paint, like some charge a Pet Deposit. That would make your residents think about this before they rush in to paint a burnt sienna color in the kitchen.