Vaquero frt sight

Could a red insert be installed in a Ruger Vaquero front sight? Old eyes need better sight picture.

With money & skill,, anything is possible.

A few different ways to go.
One, have the front blade removed, dovetail the barrel, and add a sight of your choice.
Another; Mill a section out of the front blade, and have an insert added.
Lastly,, the easiest & cheapest.
Paint the rear edge of the front blade with white nail polish, let dry, the go over the white with a green or red color nail polish. This method doesn't affect the gun in any way, and allows you to return it to the factory configuration.

Someone (Slick McCade seems to be the Google result) makes covers that slip over Vaquero front sights that may suit your needs.

Hobby Lobby has paint pens with a fine tip that makes painting my front sights easy!