At the main menu, scroll down till you find extras. From there, you will see “Pinky’s Guide to Inkies”. Every enemy you meet during the game will be shown here. There are a total of 14 enemies in the game. Here's a complete list:
Pinky
Paint Bot
Leech Bot
Blanc
Shepherd
Inky
Sergeant
Mortar
Heavy Inky
Elite
Spikey
Bomb Bot
Monster
Comrade Black
You will find these enemies as you progress throughout the game so you cannot miss them. Courtesy of Flowin 92 from the TA website.