My rubber slippers absorbed my blood...

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Well, the title was intentionally exagerated, but I just finished washing my green rubber slippers just now and I noticed that sudge turned green while I was soaping them. If there were dies that had been extracted while I was soaping my slippers, the sudge should have turned green instead of red. But to my confusion it turned red. I wonder if my slippers had been absorbing my blood all this time I was wearing them; lauhgs... Anyway what do you think? Any chemist out there that can explain what happen? Cheers all!