Embodiments of the invention are directed to a roller ball marking instrument for use with paint, a method for assembling the roller ball marking instrument, and a system for delivering paint. The body of the marking instrument includes a reservoir for storing paint. The body is coupled to a fibrous roller ball via a retaining ring. The roller balls sits within a partially-enclosed cavity in the center of the retaining ring. A least part of the roller ball protrudes through an opening in the retaining ring. Paint in the reservoir moves first through an opening at one end of the body and then through an open center of the retaining ring. The paint is transferred to the roller ball. The roller ball rotates freely within the cavity of the retaining ring and transfers the paint to a writing surface.