Which type?
The First Type fully checkered target grips had a dull oil finish.
The Second Type had a semi-gloss varnish type finish.
All later Colt Target grips had a semi-gloss surface finish.
The First Type fully checkered Colt Target grip. Dull oil finish:
Second Type Colt Target grip. A semi-gloss surface finish:
Third Type Target grip. Semi-gloss.
Colt Target grips were American Walnut.
The actual Colt finish was a reddish stain mixed with a semi-gloss finish.
The closest I've found to factory is Minwax Polyshades Olde Maple.
Usually three coats will match a factory finish.