I graduated from UCSD Muir College in Biology many years ago. At that time there were four colleges, three of which had names. 
I chose Muir because I worked full time through college and it was the most flexible at the time.
The idea at UCSD is that each college has its own personality, its own physical space and its own GE and Humanities requirements. You can check the website for in-depth discussion. Revelle has the rep for hard core science and a rigorous Humanities program, Warren for engineering, etc. AFAIK, you can do just about any major through any of the colleges. Now they admit to a particular college. A friend’s daughter is at Eleanor Roosevelt. She’s a ChemE major. She is feeling very bummed about what she views as excessive non-major GE requirements and now wishes she were in a different college. YMMV of course.