I have made antique mirrors using a spray paint by krylon called looking glass ! I don't know if it will blend right in looking at it from the mirror side ? I guess you have nothing to lose ... When using this type of spray paint , lay the mirror down , with the back of the mirror facing up . Then spray the paint in light coats !!! Do 3-4 light coats , it will dry very quickly . To protect it you can spray a dark colored coat of spray paint over the mirrored paint. Good luck !
Yes they can, but it is very expensive. Generally not worth it. If the Mirror is old - it is nice to have some signs of age in the mirror glass (Some folks won't buy a mirror with new glass in it! If it is new, it is generally not worth doing, rather replace mirror instead. It is also possible to buy Plastic Mirror replacements too. You could buy Mirror Film, or try to place foil behind or spray with a mirror spray from a can.
Hope that's of help!
Fran, You can buy spray paints made for the back side of mirrors at home improvement stores.
Yes they can, but it is not cheap. Contact your local glass and mirror shops. Might be less expensive to replace the mirror.