Color On Costa Rica 36

I have 3 copies o Scott 36, Costa Rica 1892, 2 centavos stamp. Two of the copies are the yellow shade listed in the catalog, although I would not characterize them as bight yellow— more along the lines of orange yellow or light brownish yellow—but the third copy is clearly medium brown without a trace of yellow or orange.

Is this latter shade known. I do not see a shade variance at least in Scott

This is probably a case of oxidation of the printing ink, in which case the yellow would turn to brown.

These can be found yellow orange, yellow orange brownish,even light brown.
see lots 23,24,25 for some examples.

https://www.socorico.org/auction-230.php

Many thanks for the above responses. My experience with oxidation in yellow or orange stamps is that the oxidation is variable on the face of the stamp, is easy to see as abnormal and not the typical color for the stamp etc. that is not the case with the stamp in question which just appears as a medium brown stamp as one would expect to see printed that way and without any of the give away clues suggesting oxidation. Nonetheless, given the minimal value, I will give a try at removing oxidation and see what happens.

Appreciate images shown by Perf 112, however the stamp I am talking about looks nothing like the stamps he refers to which all look to me like variation of yellow orange. This is clearly brown.

But as they say: common is common