Marking Adjustable Objective

I've had good luck with pin-striping tape (auto detail tape, etc-seems to have many names). It comes in various thicknesses and colors and can written on quite easily with a simple ball point pen. I bought a roll of light green at the local Napa auto parts for a few bucks. I saw it while I was standing in line and realized it would be perfect. I've done multiple scopes and more than half of the roll is left. I might have to put some clear packing tape over it for water protection after reading the above.