The word "colleague" is associated with the word "college". Originally it referred to a fellow member of a profession or official body. Two teachers would be colleagues. Two doctors would be colleagues. In our modern world, the term is used to describe people who work together in all fields of employment. It would, however, sound odd if we heard the term used for two people working in low paying jobs. If a construction worker called his coworker his colleague, we would think he was being funny. Hope this helps

they both have the same meaning

In my experience, 'coworker' seems less formal than 'colleague'. I agree with Kamal and Kia, they mean the same thing but I tend to use 'coworker' more often.

Thank you, Kamal.

Both mean the same. They are synonyms :)