I'm having chronic diarrhea. what are the chances that this is colon cancer at age 30 years old?

Very very low: Diarrhea is an unusual presentation alone of colon cancer. Additionally it is very very rare for a 30yo to get colon cancer. When colon cancer gets a bit advanced it can cause constipation or intermittent diarrhea and constipation or pain or bleeding or bloating. You should see a GI specialist or your regular doctor to discuss what might be causing the diarrhea and how to remedy it.

Low: The chances are low. Yet this does not mean that you should not discuss with your primary care physician or GI specialist in further detail. There are certain clues in a history we use to determine a risk profile. This can only be ascertained in a face to face discussion. This forum is subpar for this type of discussion.