[wizzwizz4]

That would imply a frequency shift, which clearly doesn't happen (mirrors don't redshift the light that hits them).

[ASalazarMX]

I balked at that too, because infinite mirrors and mirror houses also don't show any wavelenght shift no matter how many reflections they do. They do change perceived amplitude, as no mirror is perfectly reflective.

[Jerrrry]

Blue, but it's more to do with manufacturing defects and the minerals used for the mirrors.