Any color won't work. Blue and green will most definately expose your paper. Yellow LEDs work better than Low pressure SOX lamp used in the the famous Thomas safe light, known for incredible brightness due to the narrow bandwidth of sodium. But it still required a filter to remove the neon and mercury lines. The LED has a much narrower bandwidth and needs no such filter as its light is very pure. Yellow is also less irratating to the eye as your eye is most sensitive to green. Red is at the end of the range of human vision and thus requires much higher illumination levels to appear the same brightness as yellow. Amber has been the safelight standard for many years and LEDs produce this color very well. It is the second color LEDs were available in the early days. The first was Infrared, then red, amber, yellow, yellow green, then pure green in the mid 90s, followed by blue. There are two violet LEDs out now. One is a blue LED using a red phosphor and a native violet and recently true UV LEDs. White LEDs don't count as they are all blue LEDs with a drop of yellow and/or white phosphor over the die.

The problem with LEDs, or rather the marketing (profits), is the LED can last forever. Because they are extreemely overdriven they are marketed as having a 20,000 to 50,000 hour life. Heat and overcurrent can destroy and severly shorten the LED lifespan significantly.