These are the 3 types of zombies:
Normal Zombie-
Color: blue-green
Speed: medium
Health: medium
Begins Spawning: 0 kills
Suggested Weapon Type: mass area damage
Sprinter Zombie-
Color: blue-purple
Speed: Fast
Health: Low
Begins Spawning: About 20 kills
Suggested Weapon Type: quick reload, lower damage
Snatcher Zombie-
Color: bright green
Speed: slow
Health: high
Begins Spawning: about 500 kills
Suggested Weapon Type: high damage