Colour Error???

How far out does a colour have to be, before it is considered an error?
The reason I ask is that I have come across two stamps in my collection that have different colour backgrounds, but were only released in one colour. One is orange and the other is yellow. I don't think one has faded as the other colours all look normal.




Combined picture, to emphasise to difference...

The stamp is SG-661 issued in 1978 as part of an aviator series.
Any info in your Scott catalogs?

Steve

Hello Trigger.....

It looks to me that all the colors are lighter on the second stamp.....maybe sun bleached or a chemical wash of some sort.

It is a striking difference....but more than likely a freak rather than a true error.

Your stamp is listed as
Scott #675 18c yellow & multicolored Charles Ulm and "Southern Cross."

also there is there is listed
Scott #674 18c orange & multicolored Charles Kingford-Smith and Fokker "Southern Cross."

It looks like your orange & multi #675 Ulm stamp is a color error, but it is not listed.

The brown of pilot's jacket does look a little faded on the yellow stamp. Might be useful to compare these stamps to the orange color of an example of #674.

I acquired these stamps from a friend who collected when he was young. The stamps have been stored in an album since new, so I don't think they are faded.

The Kingsford-Smith stamp has the same problem to a lesser extent.



Steve

These color variations could result if the dyes used to print these stamps are not stable, at least over the course of 30 years. Even though they were kept shielded from the sun, the dyes are breaking down and losing their color (bleaching).

Thanks for your opinions,guys.
I guess it will remain a mystery.

Steve