Well good luck, but I dont see how you can expect any explanation via a vague verbal description.
Without a physical examination and tests/measurements of various physical parameters (blood pressure, extensive blood chemistry tests, etc) actually taken DURING the "green" incident, tests on the chemicals to see a full account of any trace adulterants, any "diagnosis" is of course going to be 100% pure guessing. I don't see how that could have any value to you.
The most you are going to be able to get I think will be a generalized guess of "Queasiness from coming up too much too fast." I have gotten that myself from methylone by itself. But once vomit was over I was fine. I think that's nothing to worry over, just a very common automatic "purge of toxins" reaction by the body to many too-rapid-and-unexpected change-of-state events... I think that is just some generally over-protective program, as the limbic system decides "WTF? This should NOT be happening, emergency PURGE just in case we were poisoned" Animals that had that impulse built in probably tend to live longer, hence that program survived evolution, and its in us now.
So far as the green, I know of NO mechanism that could cause the skin/blood to turn green. BLUE from lack of oxygen yes, but GREEN is always an optical illusion/impression only. Blue skin can be caused by vasoconstriction. Which can be triggered by various stimulants. Combination of Methylone with ANY 2C drug, which are all phenethylamines and this very strong stimulants in and of themselves poses a HIGH risk of a synergistic reaction, strengthening the effect many times over the individual doses by themselves. So maybe you were really turning BLUE from excess stimulant trigger vasoconstriction, and in your psychedelic state the blue just APPEARED green. You state you were having visual hallucinatory effects, so how do you REALLY know you were turning green and it was not just another visual distortion???
Actually maybe the drugs triggered some huge release of BILE into the bloodstream? Can that happen? But that seems unlikely. Especially since it went away quickly I suggest halllucinatory color distortion. Even if your liver turned off due to the drugs...no... jaundice from hepatitis does NOT happen and go away so quickly... it takes a period of days.
Also MANY MANY sources on the net have been advising for YEARS now to **NOT** snort 2C drugs due to excessively rapid effects and cardiovascular instability. DO YOUR HOMEWORK.
And methylone is well known to NOT work well or have disadvantages being snorted.
WHY DO PEOPLE INSIST ON STUFFING EVERYTHING UP THEIR NOSES? I really wish people would get over this horrible pointless dangerous silly bad habit of snorting everything.
Well that's my 2 cents guessing and warnings for the general public. Please don't take any offense at my tone, just being emphatic that's all... I am glad things worked out in the end for you and you found the experience useful. Thanks for posting about it... all honest accounts add to our collective knowledge base, so good job with all the specifics.