All the bi color, and multi color LEDs, especially through hole type, only come red and green. Or red green, and blue. And there's none with yellow. I know as a builder and designer of outdoor model railroad signals, and live steam scale signals, this would be a godsend if they were available. Also the red is so dull, they're hard to see, even with stepped lenses. To get them to mix with green, you have to put so many resistors to get red and green to blend for yellow, that you lose light. What's an alternative?
Electronic – Why are there no high intensity tri-color LEDs that have red, yellow, and green
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Best Answer
There are few tri-colour LEDs with yellow, because you can make yellow from red and green. This is the way that all multi-colour LEDs work for most other people on the planet.
If there is a problem with your specific LED, or your specific eyes, then that's a problem that has to be addressed by getting a new working LED, or visiting the optician.
According to wikipedia, 2% of males have protanopia or protanomoly, an absence or a shift to higher frequencies of the red receptors, which would render red LEDs 'hard to see'.