Most of us live our lives blissfully unaware of the science behind how we perceive color. No need to concern ourselves with contrast, saturation, and other words you'd find in Photoshop's drop-down menus. If a t-shirt looks white, then it's white... right?
As it turns out, laundry detergents use one weird trick to make white clothes seem brighter: Fluorescent whitening agents, or FWAs.
These chemicals absorb the ultraviolet light in natural sunlight and illumination cast by incandescent light bulbs, and render it in a bluish hue. This dulls certain colors—most importantly yellow hues—making your t-shirts appear as a brighter, happier white.
Why does this matter? Well, a study published in LEUKOS, The Journal of the Illuminating Engineering Society of North America, showed that FWAs are ineffective under most LED light sources. Since LEDs don't emit UV light for the FWAs to absorb, your clothes aren't getting the benefits they've traditionally provided.
In other words, while incandescents literally put things in a positive light, LEDs show a fabric's true colors. Incandescent light bulbs are being phased out across America, which means these soothsaying LEDs will begin to pop up everywhere in the months and years to come. End result? Those pit stains will be a little more visible.
Still, the same study found that LEDs that have been tuned to emit violet hues can have the same effect on FWAs as our beloved incandescent bulbs. The most common LEDs on the market today don't do this, but it could happen in the near future.
Until then, we'll just have to live with the dull, sad truth. The veil has fallen. There is no going back.