From: "Phil Payne" 

"John Beckett"  wrote in message
news:v52ku2hvqrv67f5mdvka1bf878r6rrdn45{at}4ax.com...

> I think that the light emitted by a LED is in a very narrow band of
> frequency (at least it was, when I learnt about LEDs). So a red LED
> emits light (almost) only at the red frequencies.
>
> Therefore, you can't just filter it to whatever colour you want.

And a white LED?

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