I'm not sure if it is organic or not. I do remember that the Metal Gear Rays in MGS2 "bled" as well, and there was no mention of them containing any organic material. Personally, I think it's just artistic license, meant to make the Metal Gears seem more like monsters (this, by the way, is consistent with Metal Gear Rex, Ray, and the Shagohad "roaring").
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it's hydraulic fluid... mechanics have it colored red so that they can see it when it's broken.
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Good point. I still think the sprays are done as artistic license. As Gromnir has said in the past, the Japanese tend to love giant monsters (this is not racist, but a cultural observation based on stories).
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Man, that's racist. I'm reporting you.