two pictures are below, one of a clear shirt, and another of the same shirt as viewed in a foggy bathroom mirror.
Now, putting on this shirt in the morning, I was very excited to see that there was no purple visible in the mirror’s fogged-up reflection, but the blue lines are fine (this was even more exaggerated a minute or so before I took the picture, look toward the top of the image for the most severe effect).
Even if you know it is there, and wanted to, you can’t really see any purple stripes in the fog. I think the problem is almost the same as astronomers had seeing into forming stars- dust (or in our case, condensed water vapor) blocks light. The reason for this would be that shorter wavelengths are more easily blocked than longer ones (purple being of shorter wavelength than blue which is shorter than green; yellow; orange; red; and so on).
Astronomers solved this problem by instead of looking at the visible wavelengths, building telescopes which record (higher wavelength) Infrared light data. They could then see through those bothersome clouds of dust surrounding all of the cool stuff going on at the birth of a star.
Unfortunately, I don’t have infrared-vision yet, so for now I’ll have to settle for just not looking for purple in a foggy mirror.