I would say that the color of the oil tells...something. If the oil is changing color, it means that something is happening with the oil. Although this is the normal transformation, if you are comparing apples to apples, then maybe you can take something out of it. If you take a neglected engine and do a flush only with new oil, the first time you drain the oil it will be darker than the subsequent flushes. But i believe that the intention of the OP is to say that you can't determine if the oil is good or bad just by looking at its color. The oil on my ethanol car always looks brand new on the dipstick, that doesn't mean it is still usable after the end of an OCI.