Apparatus for marking a blood vessel for use as a bypass graft in a patient includes a preparation plate for supporting an isolated blood vessel that is in a state for anastomosing to the patient. A stencil plate is configured for overlying the blood vessel and preparation plate, wherein the stencil plate has an opening adapted to expose a portion of the blood vessel to a dye applied through the opening. The stencil plate around the opening is adapted to shield the blood vessel from the dye. A dye applicator is configured to direct a metered amount of the dye through the opening and onto the exposed portion of the blood vessel, preferably as a mist. Preferably, the opening is a lineal slot for creating a guide line extending longitudinally along an outer wall of the blood vessel.
