the only way I know to do this is to figure out if you need to strip the finish or finish over sanded finish then mix a compatible product with a compatible coloring agent with your finish and lots of compatible solvent so its real thin and spray light coats until it comes out the right color, With lacquer finishes I make my toners 10% store bought stain, 10% clear lacquer and 80% Lacquer thinner. My guess the existing finish on the stock will need to be removed and the new applied. I think this job is best dont by professional but if you have something to practice on you could come up with a possible solution. Check with a coatings manufacturer like Sherwin Williams to find compatible products. Sorry this is long and complex but your simple project is not so simple a task. Paint is a more viable solution.