It does not cover how to destroy the guardians that will try to keep you from the keys either. A rather beautiful color.
Some people consider it a symbol of love.
A Key Card is a small object, found in DOOM, that looks like a computer add-on card. They come in three colors, red, blue, and yellow. A Skull Key is a small object, found in DOOM, that looks like a small skull. As with the Key Cards, they come in red, blue, and yellow. Skull Keys function identically to Key Cards.