Creating topics in messenger

When I was discussing with my friends about our upcoming Yosemite trip using mobile group chat application, I noticed that we were spending a significant amount of time just to figure out which topic or subject we were talking about.
Different from actual conversation, we check messages in different points of time. Also, there are only a few ways to refer to the previous topic using variations of this and that. Observing us keep referring to this and that and keep getting confused with which subject we were talking about, I wanted to explore possible solutions for this problem.

The idea was: what if we can start a topic inside the messenger by assigning a message as a start point of a discussion?

There were three main points I was trying to achieve.
1. Color code message threads so that users can see which messages are grouped as a topic.
2. A topic should be assigned with interaction that is as simple as possible.
3. Without changing the chronological appearance of messages, the solution should allow users to see the threaded messages as a group.