I decided to try an old Megatech RC submarine out, it uses some 3-5mm LED lights for illumination, and they looked like a cool green fluorescent!
I assume they tried to run them at high power, but they eventually greened out.
Is that what happened?

Sounds pert near right, I've overdriven some white LEDs for q short period, then on normal power they were green and blu, like ye olde mercs.

Maybe for blue the phosphor got burned off.

The blue part of the spectrum goes directly from the chip, the phosphor then radiates only the rest.

With the transparent plastic LED's is the plastic uses to brown out (high temperature plus high intensity of energy photons from the chip), blocking mainly the blue. When combined with the older high CCT phosphors, it may end up quite greenish.

Oddly, it still looks clear, not browned.

The browning affect just a very thin layer just around the die, you practically won't see it (maybe looking in details, when you have some not degraded reference to compare).

The browning affect just a very thin layer just around the die, you practically won't see it (maybe looking in details, when you have some not degraded reference to compare).

Maybe that's what happened, but maybe they did that intentionally to have the light go further in the water.

I doubt they will do special LED batch for a toy or so, the related tooling is just way too expensive. Plus when the water is clear, it pass all the visible. And when it s not clear, it depends on the exact contamination...

I can't be 100% certain, but I think the new 4100k LEDs installed back in June may be showing hints at a very very very slight greenish color.  I'm going to keep an eye on it.  I think I might like this, could turn out to look like a MV <grin>