Bubbles will appear Red when someone other than the contact’s assigned User has sent a personal one-to-one text to the contact.  Think of the message history displayed in the Record as a conversation that is supposed to be taking place between two people - the User who owns that contact and their customer.  If another User should jump into the conversation and send a message to the contact (without taking ownership), then their bubble will be colored Red. It would be like a 3rd party jumping into the middle of an on-going telephone conversation.  By coloring these types of text bubbles Red, it makes it easy to distinguish when a normal chat occurring between a contact’s assigned User and their customer is interrupted by a 3rd person.  The Red bubble is immediately displayed in the contact owner's Record to inform them that this other conversation took place.

Brown bubbles are never sent to the contact.  They are simply Notes that can be added to a contact's conversation history by any User on the system at anytime.  These Notes are inserted into the contact's message history with a time-date stamp showing when they were added and who authored the Note in case further details are needed.