Some
copper (or copper plated)
coins are described as "red", referring to the dark red colour of a newly
minted coin.
Over time copper coins
tarnish and begin to turn
green. Constant handling removes some of the tarnish and as a result the coin will appear
brown.
Collectors often refer to a coin as "red" to indicate that it has been handled very little and not exposed to any
elements (like
water) that would cause it to tarnish. Because the metal is so soft, it is impossible to clean a copper coin and return it to a "red" state.