after fighting with ls mates over this i finally have proof! It's Yellow! Not Grellow! start saying it right! whenever i see someone call it grellow, i cringe...
Quote:
Spectral Alignment
There exist five lights in the existential spectrum. Their alignment values can be enhanced to produce the following benefits:
Blue: Increases reward quantity.
Red: Increases reward quality.
Yellow: Increases experience yield.
Green: Increases cruor yield.
White: Increases chances of atmacite and periapt obtainment.
The alignment values for the above can be enhanced via the two methods below.
link here
they even have a very clear picture of it being triggered close to the bottom of the page.