A colon is a very useful punctuation mark that has only a only a few specific uses.
Be sure to have a good reason when you use one in your writing.
Use a colon:
- To separate hours from minutes (2:30) and show ratios (5:1)
- To punctuate the greeting in a business letter (Dear Madam:)
- To separate chapter from verse in the Bible (John 3:16)
- To join two independent clauses, if you wish to place emphasis on the second clause. (Use this one sparingly. It is easy to get it wrong.)
- At the end of an independent clause to show that a list, an appositive or a quotation is to follow.
Have a great day!