I don't think tinting will work on the mirror, it appears what will happen is that a double image of the reflection it's imaging will be created. The only way to do it right is to take out the old mirror and install a new mirror that has the tint before the mirror but before the glass. I'll try to search around or call my local glass shop to see if I could have mine replaced. What I'd do is remove / break out the old mirror in the micro-mirror and then have a new quality blue tinted mirror placed in. Shouldn't be hard nor cost much. But we'll see.
From a thread:
tinting your rear view
"The only way to "tint" a mirror would be to apply the tint between the glass and the reflective surface (impossible). When you look into a mirror, you are looking at the surface behind the glass. If you put a piece of tint on top of the glass, the image you are looking at is entering the glass, reflecting off the reflective surface, then reflecting off the inside of the tint, back to the mirror surface. You will always get a double image. The only way would be to find a company that makes mirrors, and keep in mind, I have no idea if this is at all possible, and see if you can have a "tinted" mirror made. If that is possible, you could bring your current mirrors to them, they can cut the piece you need, and you would have to get the glass removed from the backing of the mirror assembly and the new glass glued back into place."