We played around a bit with trying to control LED Brightness with variable resistance in one of our products, found that the only real way to get a decent control was to use a pulse width modulated voltage source. With the pulse width varying from anywhere from about 100% on to about a 20% on, 80% off, the control was almost as good as a pot with an incandescent bulb. But a bit pricier and more complex.
First, run them at less than 20 ma to reduce brightness.
Second, a wash of orangeish paint. Theater people call this “bastard amber,” and it’s a standard color to “warm up” the harsh bright theater lights.