Usage of colon

Bangkok bomb: Thai capital reeling after deadliest attack in years
- The Guardian , August 17 -

I am trying to use colon correctly but I am confused all the time so could you tell me how to use it correctly and why the colon is used in the title and which one can I apply to in this case?

Colon

A colon is used to give emphasis, present dialogue, introduce lists or text, and clarify composition titles.
Emphasis—Capitalize the first word after the colon only if it is a proper noun or the start of a complete sentence. (She had one love: Western Michigan University.)
Dialogue—Write the speaker's name, followed by a colon and his or her statement. (Reporter: What is the Western Edge? Dunn: It is a strategic plan for promoting student success.)
Introduce lists, text or tabular material—Capitalize the first word after the colon only if it is a proper noun or the start of a complete sentence. (Our future is dependent on three things: sustainability, diversity, and enhancing our strength and health.)
Clarify the titles of books, lectures and other compositions—Use a colon in titles that express two parallel ideas. The words on either side of the colon should be able to stand on their own. (He wrote "Crisis Management by Apology: Corporate Response to Allegations of Wrongdoing.")

or

colon used before list Williams was so hungry he ate everything in the house: chips, cold pizza, pretzels and dip, hot dogs, peanut butter and candy.
colon used before a description Jane is so desperate that she'll date anyone, even Tom: he's uglier than a squashed toad on the highway, and that's on his good days.
colon before definition For years while I was reading Shakespeare's Othello and criticism on it, I had to constantly look up the word "egregious" since the villain uses that word: outstandingly bad or shocking.
colon before explanation I had a rough weekend: I had chest pain and spent all Saturday and Sunday in the emergency room.
Some writers use fragments (incomplete sentences) before a colon for emphasis or stylistic preferences (to show a character's voice in literature), as in this example:
Dinner: chips and juice. What a well-rounded diet I have.
Thank you so much as usual in advance!