> The blue light reduced the yellow stain substantially more than hydrogen peroxide or UV exposure. In fact, UV exposure generated some new yellow-colored compounds.

Here's the key piece of information for me, it's not just light doing this or higher energy blue being close enough to UV to get things done, the blue light tested outperforms UV at destroying some of these yellowing compounds.

It would be nice in followup research to see Figure S8 [1] with an additional dimension for irradiation with various frequencies, not just 445 nm.

It looks like Amazon has some "therapy bulbs"[2] close to the correct frequency for $30, now I wish I hadn't thrown away some of those old yellowed pillows so I could do some science.

1. https://pubs.acs.org/doi/10.1021/acssuschemeng.5c03907

2. https://www.amazon.com/Aumtrly-Light-Therapy-Irradiance-Cove...