Quote:
i found black but blue print I cant found..
This stamp
should be green, with some variation in shades. There may be proofs or essays in black (I'm no expert), but it shouldn't exist as an actual stamp in that color. As Don stated, the blue is due to discoloration.
To answer qaman's question, I'd keep something like this as a space filler until I found a better specimen. That's assuming that I got it for free; I certainly wouldn't buy a stamp in this condition.* And even though some of the earlier stamps in my U.S. album aren't in the greatest condition, I don't currently have anything this bad in there.
* Okay, I've spent $12.50 on a Volapük cinderella from Amoy, circa 1890s, that was in almost as dreadful condition. But things like that are super-rare, and I had to have it.