4 Oct 2004
The change to green does not end even if the Leprechaun leaves the battlefield.
4 Oct 2004
A Leprechaun with Protection from Green can be blocked by a creature (since it is not green at that time) but will not take damage from the creature (since it is green during the combat damage step).
4 Oct 2004
Creatures change color as a triggered ability upon the block being declared.