Why is there a purple behavior tag, and a blue behavior tag? What is the difference between the two types of tags?

Behavior tags in purple are tags attached from the system (interact with Marketing messages, submit from landing pages, interact with social media posts). Once the tag is attached, it can no longer be removed.
Behavior tags in blue are tags attached when importing a file by the user or manually by the user by accessing the profile editing section. The blue tag can be removed after attaching.