The literal explanation of "betting on red" is referring to the game of roulette, in which you can place a bet on the colours red and black or on specific numbers. You might also already know that Macau is very famous for it's casinos, often being called the Vegas of Asia. In the non-literal meaning of "betting on red" in the titles of this article, it is difficult to guess the full meaning, without having read the article. However, if I had to guess, I'd say it referring to both or either the country being an autonomous region of China (where, as you know, red is the colour of the flag) and/or how "being in the red" is the financial term for being in debt.

I don't understand it, either. It's being used as a metaphor or a figure of speech. Literally, "betting on red" refers to the game of roulette. A which a ball can fall into one of 38 numbered slots (1 to 36, 0, and 00). Half the numbers are colored red, half are colored black. Many bets are possible, but common ones are "betting on red" and "betting on black." Here, I am sure that there is some kind of pun and that red must be associated with a political party or faction.

There's a play on words going on. There is a reference to the gambling of Macau with the 'red' (you can gamble on red for instance on the Roulette table). Separately, red is also a more general symbol of prosperity, good fortune, so there is a reference here as well. Also, red is a symbol for China or the communist party. To know the exact meaning of the title, you need to read the article. But I would guess it is related to one of the above. The first paragraph of the article would reveal the exact meaning or reference.

This is a term from roulette. They chose this expression because Macau is famous for its casinos. It also has the double meaning of red being the color of the Communist Party.