[Willard]

SMT, I would say wise move on your part. I'm not sure how Colt finishes their wood grips, if in fact they are factory. If they have the Colt medallion, they probably are. If they are, I would contact Colt Customer Service as to their care.
I know, that Hogue recommends removing their wooden grips before cleaning. They also recommend using furniture polish on their grips. Using a cloth to buff them off. They use Carnuba Wax, and clear lacquer in the checkering.
You can use an old toothbrush, with soft bristles to clean inside the checkering.

 

[BrowningsGhost]

Rosewood's are very hard, dense and oily woods that very durable require very little finish.
As is the case with tool handles made from rosewoods, they usually finished with shellac which is not affected by the oils in the wood but are sensitive to alcohol (which is shellac thinner). They shellac will also keep the grip or tool handle from feeling plasticy.

Mass manufactured grip are more often uses a oil/varnish blend which has a contains a film like polyurathane that is more durable and less susceptible to solvents.
A microcrystaline wax (i.e. rennaisance wax) or paste wax (i.e. minwax) will add a layer of protection. A little goes a long way, and remember wax is a lubricant, which is the opposite of a "grip".

FWIW, I use Ballistol as a CLP which claims to be wood friendy. It seems alright on my 1911 and My P225 which are the only pistols i have that have wood grips.