The Green Slime is the weakest variation of the slimes, dealing moderate damage to most characters, and is also very slow moving.
The 'Boss' variant of the slimes, he is a very large green slime. More information is found at Giant Slime.
The Red Slime is the most dangerous variation of the slimes. They move very slowly, however they deal high damage to even the most heavily armored characters. These should be dealt with quickly, as they can seriously affect the outcome of a battle if taken lightly. These slimes also can ignore armor, thus dealing so much damage.