Are colorless Pokemon considered a 'type' in regards to Xerneas' "Rainbow Force" attack?
Yes, Pokemon may be of a "Colorless" type.

Other known variants



x2
-20

Rainbow ForceThis attack does 30 more damage for each different type of Pokémon on your Bench.



Power CreationIf this Pokémon was healed during this turn, this attack does 80 more damage.
Are colorless Pokemon considered a 'type' in regards to Xerneas' "Rainbow Force" attack?
Yes, Pokemon may be of a "Colorless" type.
Will a multitype Pokemon such as Golurk with the "Double Type" Ability count for two different types of Pokemon for Xerneas' "Rainbow Force" attack?
Yes, Rainbow Force checks for the number of types of Pokemon on your Bench, not how many Pokemon there are.
For Xerneas' "Power Creation" attack, does moving damage counters off of Xerneas to another Pokemon count as "Healing"?
No, moving damage counters off a Pokemon is not the same as healing damage (similar as to how moving damage counters onto a Pokemon is not the same as doing damage to it).
For Xerneas' "Power Creation" attack, do I need to heal all damage from Xerneas in order for the attack to do +80 more damage, or can I just heal some damage in order to get the benefit?
As long as you have healed any damage from Xerneas this turn, you get the bonus damage effect.