Yes, you can undeniably pursue economics honors from any college, even if you didn’t have Economics in your 12th. The first semester in economics ug degree is dedicated to the basic and fundamental understanding of the subject, which is also taught in school. Thus, even if you have not studied the aspects of it in school, the college you are part of will certainly cover the topics you still have to know about.
But if you are planning to do a course in Economics, it will be better to make yourself familiar with the basic concept of the course. Pick up some books on Economics after you are done with your entrance examinations if you are planning on giving any. My friends with Economics degrees suggested the following books that you can begin with.
These are to name a few. You can likewise add on more.