Most white LED's are in fact blue diodes coated with a (mix of) phosphor that emits a version of a white spectrum when excited by blue light. In theory they don't leak the blue light. (in practice, I'm sure some escapes. But white light includes blue, so I'd assume the better products compensate.)
Of course fluorescent lights are a UV emitting plasma that stimulates phosphor to generate white light. This leakage seems to me to a bigger problem....