Here's why:
* Collective nouns refer to a group of things considered as a single unit (e.g., team, flock, army).
* "Colour" refers to a property, a quality, or a sensation. It doesn't represent a collection of individual things.
Example:
* Collective noun: "The team is playing well." (Team represents a group of players)
* Not a collective noun: "The colour of the sky is blue." (Colour is a property of the sky)
Let me know if you have any other questions!