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 initial public offering valuing the gaming company at $7.6 billion. 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.