Brown paint

[dfatih]

Why is the back of a mirror traditionally painted brown? Does it aid reflectivity?

[tartanwiz]

Any paint over the reflective coat will work (without it the mirror would be semi-transparent, like a two way mirror or reflective window), and I have seen all kinds of colours used. Brown is traditional probably because they used to be hung on dark wooden furniture or free-standing frames of teak, mahogany, etc.