Help With Hungary Scott#319 (?)

This is my first post here - I hope somebody can help.
I could not find any information about this stamp.
It looks like normal Hungary Scott 319 (Harvesting wheat, 25 fillers, with red overprint and big black overprint). Everything is normal except color. Color of normal 319 is stated in Scott as "dull blue" (and I have one of those), but this stamp has completely different color - looks more like the next one (Scott 320 - olive green).
So - any idea? What is this: Olive Green #319?
Thanks!

Welcome to Stamp Community Family, igopp!

Please post a picture.

Does this mean that it has watermark too? If it has no watermark, there is a possible explanation... A picture would be useful.

On this picture you can see this stamp side-by-side with normal color stamps (with and without overprints).
And yes - I can see some watermark, but not sure about exact type.

It was probably exposed to strong light for a long period. It can be seen that the red overprint (Magyar Tanács Köztársaság) is paler too.
There were made color proofs of the original 'Harvester' stamps, the majority are unperforated, some on coloured paper. There are olive 25 filler colour-proofs, perfed 15, but it`s on plain white UNWATERMARKED paper.
This one is colour-changeling.

Agree with Wadmalatz -- it's most likely a color changeling. The color and both overprints are significantly faded, and the paper is clearly discolored.

Well - color fading is definitely a possibility, however this color looks definitely different (not just faded). My picture is not showing that clearly - when I get home today I may try to take another photo with better equipment.

The thing about color changelings is that they may change to a very different color. It depends in part on the ink pigment used -- different components of the color may fade/change unevenly, making it not only "fade" but "change color" as well. "Fading" was probably a bad choice of words on my part, as there are plenty of other mechanisms that cause color change; but yes, certain stamp inks can fade into an "apparently different" color. Color changelings in which shades of blue turn grayish are not unheard of.

The toned/discolored paper indicates the stamp has been improperly stored for an extended period at one time in the past. So a lot of things may have happened to change the color. Unless somebody can dig up some special color issue not listed in the major catalogs, I'd be surprised if this was anything but a color changeling given the condition of the stamp. This is why we asked for a picture, because the condition of the stamp reveals a lot. You had stated in your original post that "everything is normal except color", but your picture indicates otherwise.

Feel free to post another pic if you think a new pic would more accurately reveal your stamp condition and color.

I guess you are right. New photo shows some traces of blue color (specifically on the top). It is just amazing how color could be misleading - looks almost the same as 40f stamp!
Thanks everybody for your help!

Glad you got your answer/confirmation. Great additional pic, thanks!