Abstract: A method and procedure for color coding cuvettes used in laboratory tests without contaminating the interior thereof or changing its binding properties is described. In the procedure of this invention, transparent plastic cuvettes are utilized which are flat bottomed and have a depending rim surrounding the flat bottom. The depending surface of the rim then has color applied thereto by a conventional technique either hot stamping, or by ultra-violet cured silk screen printing. In either event, a colored surface is formed on the rim. The transparent walls of the cuvette then by light pipe effect give the appearance that the color surrounds the upper opening of such cuvette when in fact the opening is of transparent plastic.