is it possible to change the color of a blue LED light source? Can the blue be filtered out to make white or some other color?


No, you can't. Most of the light emitted by a standard magnesium-doped gallium nitride blue LED is in the blue part of the spectrum, as shown here.

Blue LED spectrum

(Image from Science Direct)

So if you filter it to make it look less blue the resulting light will be rather dim.

Here's a chromaticity diagram from Wikipedia that shows the colours corresponding to various wavelengths. The numbers it shows are nanometres, so they're 10 times smaller than the Angstrom units used in the graph above.

Chromaticity diagram

  • 1
    $\begingroup$ One can, of course, use phosphors to alter the color. $\endgroup$ – Jon Custer Dec 1 '18 at 16:23

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