Sometimes we get calls to say that the color the customer received is not the color they ordered. Although we wish we never made mistakes, it does happen (rarely :) But sometimes, it's the mass tone causing the problem. Mass tone is the color of the ink in the container, or the color of the body of the ink. It can be really difficult to tell a yellow from an orange for example by just looking at the color of the ink when not printed. The ink film needs to be close to the density you would print at to accurately tell what the color really looks like. A quick test to determine what the ink will look like printed (not exact, mind you) is to dip your fingertip into the ink, then tap it out on a hard surface like your metal or glass mixing surface until the film is very thin on your fingertip, then onto a piece of paper. It takes some practice to get it right-not too thick, not too thin; but with a little practice you can get a fairly good idea of what the printed color of the ink will be. Happy Printing!