These are usually blue. I see no mention in SC about a different color. Doesn't appear to be faded or otherwise altered. Also, I don't see one of this color for sale on HS. Info?
I would suggest its a type of color changeling. Exposure to particular contaminants can result in color change. if you look closely at the area around the text at left "POSTES", particularly near the top above the P it appears to show some similar color to the stamp below it.
There is a proof that is similar to color, but it is not perfed.
![Can208u[c]](https://www.hipstamp.com/forums/uploads/imageupload/112/WSVOFPNNVVLY.jpg "Can208u[c]")
![Can208u[b]](https://www.hipstamp.com/forums/uploads/imageupload/880/VXSB20KWZ3OG.jpg "Can208u[b]")
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There is a proof that is similar to color, but it is not perfed.