1893 Columbian Issue, Error Of Color?

hallo, if this stamp 4c Blue, Error of Color, Used (Scott #233a)?







printerror or external damage?

Thanks.

233....
damgae/stain

No, and not close. All anyone has to do is place any questionable four cent next to a one cent Columbian. If the color does not at least approximately match then it's not the error (there are two shades of the error).

That damage/stain spot looks like the ultramarine ink had been bleached or sun faded, lines of ink are still present.
The Error of Color 4 cent Colunbian is, as has been mentioned, more the color of the 1 cent Columbian.....
from the U.S. Philatelic Classics Society 1987 Chronicle: 138
"While printed with ink using the same Prussian blue colorant, the 4¢
error is not exactly the same blue as the I¢ Columbian."

and Chronicle 135
""One-cent. - ' Co lumbus in Sight of Land ,' after the painting by Wm . H. Powell ," and
"Color, Antwerp blue ."

The two shades that revcollector mentioned?
Here's the 1 cent Columbian for comparison.