The color change effect from fingerprints is most pronounced at the
lower voltage colors. The lower the voltage, the thinner the oxide
layer, and thus the greater effect of the ‘extra’ layer imparted by
skin oils. So if you run up into the higher voltage colors, you’ll
have less problem. Of course, those colors are less brilliant. So
there’s a tradeoff.
Any coating you add is going to change the thickness of the clear
layer that’s doing the reflecting, which is what’s causing the
apparent color. So anything you do is going to mess with the color
to some extent.
The oxide itself is pretty tough, especially in relation to chemical
cleaners. I’ve always found windex or other non-abrasive glass
cleaner to do a pretty good job at getting the oil off. This leaves
you with a clean, bright surface. Until somebody touches it again. I
also sand/beadblast the surface to give it a non-directional matte
surface, which helps brighten things up. RMS’s "Multi-etch’ solution
does a pretty good job at etching the surface to increase the
brilliance of the colors as well, so definitely give that a try.
About the worst possible surface, from a color point of view, would
be a tripoli or rouge’d finish. It’ll be blazing bright from one
(and only one) angle, and stone dead from most others. (and
fingerprints will stand out like a sore thumb.)
Remember that titanium isn’t really all that strong. It’s tougher
than silver, and has some spectacularly peculiar working properties
that give it a bad rep, but it’s not a whole lot harder than nickel
silver, or hard anodized aluminum. And the colors will scratch if
subject to abrasion or wear. So pay attention to how you’re using
it, and what you’re asking it to do. Make sure that what you ask of
it is something it’s actually good at. “brooch for fancy night out”?
Definitely. Wedding ring? Probably not, unless you like grey.