In this instance I'm using red duct tape. Measure 1.5cm by 1.5 cm on your duct tape. This is the area of a Rubik's cubes' sticker. Make sure it is not too big so that it goes over the cubie.
Cut this out and stick it on the matching coloured side on your Rubik's cube.
I would then recommend writing your initials or something on your Rubik's cube so that you know it is yours.