Red ocean means to compete head to head in an established market. Companies cannibalize each other and profit margins get slimmer. Red ocean, because that's the color the sea turns into when the sharks go at each other. In business terms, companies begin to bleed money and only the strongest survive.
Blue ocean means to differentiate oneself and create new values. Sidestepping the competition in order to sell to consumers who are underserved by other companies. By being the only company to address a certain demand, the profit margins are high and the growth can be huge.
In a red ocean, the company that has the most resources usually comes out on top. That's why it would be wise for a company like Nintendo to not directly compete with Microsoft who have an enormous amount of money.
That's why I feel so bad for Sony. Any market MSFT wades in turns into instant red sea. They got jaws and they are after blood.