"Gethsemane" means olive oil press.
When people crushed and pressed olives, the extra virgin, purest oil would come out first, and it would have a reddish colour due to oxidation. This was the oil used in the Menorah (Temple candlestick.)
So when scripture says Jesus was in the garden of Gethsemane, and his sweat fell to the ground like great drops of blood, it is describing how Jesus is being crushed with the weight of our sin, like the olives in the press.