color coded light switches

if you are like me you probably have dozens of these in your house: several light switches packed into a single or double gang wall outlet. To this day i still cant remember which one of these switches works the hall and which one works the staircase. Why don't they simply change the color of the actual switches. even if only slightly. (ie grey, white, beige, etc) this simple change would probably help me to remember which switch goes to which light (grey hall, black staircase) but probably it wouldn't and i would just have spent a bunch of money and time on something that looks dumb and i would occasionally have to explain to visitors.