Why are there no high intensity tri-color LEDs that have red, yellow, and green?
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'.