If you want to apply a little oil under them for corrosion protection, that's fine...but not wholly necessary, unless the coating is scratched.
The color will change with use - I don't know that there is any protection against that, as anything you apply to protect it will also darken it. (I have been known to rub some TuffGlide or 3 in 1 oil on new micarta scales to deepen the color. Let it sit, then blot it well to remove any excess. Occasionally, the 3 in 1 will leave them a little slick; but I've never had that last more than one use, especially if the handle is fully exposed after blotting.)
The micarta will be unaffected by water under normal cirumstances, so there is no real need to protect it.