By Malathi Nayak SAN FRANCISCO (Reuters) – King Digital Entertainment Plcs colorful Candy Crush Saga has gone viral on smartphones worldwide, but the company may struggle to replicate that enthusiasm with its upcoming $7.6 billion initial public offering. The flotation this week will be closely watched in the fast-growing $17 billion mobile gaming industry, which is keen to emerge from the shadow of Zynga Inc, which has lost half its value since its 2011 IPO valued it at $8.9 billion. The red flag for this IPO is that Kings revenues and fortunes are built on one game, Michael Yoshikami, chief executive of Destination Wealth Management, said.