The action goblins unlock with the completion of not one, but two different partisan task sets per goblin.
Aqua: Ferrott the Dream & House of Thule (main floor).
Purple: The Library & Erudin Burning.
Tan: The Well & The Grounds.
Red: Miragul's Nightmare & House of Thule, Upper floors.
Green: Morell's Castle & Sanctum Somnium
Blue: Fear Itself & Al'Kabor's Nightmare.
So, if you want a particular color, there you go. =)
Edited, Feb 24th 2016 10:44pm by DRINALwoodee