A stamp collector who specializes in collecting 19th century U.S. stamps, stationary, and postal history keeps running into the issue of what colors should the authentic stamps he collects actually appear as? The colors seem to vary making it difficult for him to expertize these stamps on his own.

This collector owns various color guides ranging from the inexpensive to the rather expensive range. What frustrates the collector even more is that the colors shown in the various guides are just as varied in their own right, which doesn't help him in his self-expertizing efforts.

So how does a professional stamp expertizer determine the proper color for a particular stamp or envelope? The task of an expertizer is to decide is the stamp being examined does or does not match a given color--normally on that is listed in the catalog and within other's experience. Strictly speaking the expertizer is not "determining color" except in a very narrow sense.

We will use the Scott 10 as an example of color issues. In dealing with the color issue, you first need to come to a conclusion that the stamp being examined really is an imperforate example, and not an 1857 example with the perforations cut away.

Next you will need to consider the fact that genuine Scott 10 stamps have to be from a certain plate, while Scott 11 stamps were printed from different plates with different characteristics. So being able to plate these stamps is a good starting point As to color, it would be recommended to compare the stamp in question against known examples and against the R.H. White Encyclopedia of the Colors of United States Postage Stamps.

This work includes color plates that are the gold standard for identifying colors on U.S. stamps. In 95 percent of the cases, the answer will be clear, but there are occasional stamps where color clarity is not to be had because the stamp has been altered on purpose, or by accident. "Accident" could refer to being "weathered," such a prolonged exposure to sunlight or having had a mug of coffee spilled on it.

If the stamp has been altered, that has to be noted on the expertizer's worksheet. And the determination of what catalog number it might be is going to be a judgment call. The rule of thumb for stamp expertizer's is that the stamp should be identified as the least expensive or most common variety of the possibilities, unless the expertizer is certain otherwise.

But in the rare cases where the stamp hasn't been altered and the color is not clear, and the plating is not clear as well, the expertizer has to decline an opinion, as the standard is that the expertizer has to be 100% certain in his professional opinion.