whats happening is a couple things...
first the machine is breaking or bursting the outside perimter of the trimcombes , this is common..
secondly the burst tricombes are now getting smeared all over the surface of the buds with the help of the olive oil..
have you ever tryied olive oil to remove resin from your fingers.. it works great and also turns the oil dark and it rolls off into little balls or tubes like a snake shape but very small..
thrid.. have you ever made hash from kef , bubble or even scissor hash .. its usually clearish to some respect or green with fresh Chlorophyll .. But once you start to work it with your fingers or press it , compress it it starts to turn black like afgan hash
well that because the tricombes are getting popped.. once they pop the protective bubble is damaged.. So the next thing that happens is OXIDATION . when it oxidizes it turns black.. thats why hash is black..
but buds are never black because the actual structure of the buds protects the glads from damage...
so the olive oil is helping spread the oxidized glads all over the buds and also the oil is helping to dissolve the other glands as well which will also oxidize...
just remeber air is the oxidizer, so popping the glads means air gets to them, turning black...
the word oxygen its self has a clue in it.. OX , OXIDIZE