TELL ME
Every time I see a wacky internet fight over some niche science adjacent topic, I think of a better, cleaner, more controlled test that could plausibly settle the matter, then do nothing with that information.
The most recent one was Sugarologie vs. How To Cook That on the topic of blending meringue based buttercream frostings in order to darken the color. Sugar believes that the important difference blending makes is causing the dye to fully mix with the water droplets in suspension in the butter. HTCT believes that the important difference blending makes is removing a significant portion of the air from the icing.
My proposed test is to make three icings. In all icings, the butter will be blended before addition. In the control icing, dye will be added to the finished icing, then stirred in. In the butter theory icing, the coloring will be added to the butter before blending. In the counter butter theory icing, the dye will be added to the meringue, before the butter is added.
If air theory is correct, all icings will be a similar shade. If butter theory is correct, only the butter theory icing will be significantly darker. If something else happens, I think that implies neither theory is supported by the test, but I'd also be confused, so I'd probably think about it a lot more.