Ive done a few,
One workmate, a real PITA, hed been sniping at me for a few days, no mallice, just continious, He left his boots on top of his locker, and thay was too much temptation, I have a small pot of GREEN water based analine dye powder, a good dose inside his boots resulted in him having what looked like a pair of DAYGLOW socks on his feet, This ended up with him having green feet for 2 weeks, and his missus made him sleep in socks all that time so there were no marks on the sheets,--------OOPS.