Looks like the rumors are true the gold Mario ammibo is happening and is exclusive to Walmart. Good luck in trying to get it, because it sold out within 5 minutes on Walmart' website , full details below :

Nintendo News: Nintendo Gives Fans a Golden Opportunity to Own a Cool New Mario amiibo

Super Mario amiibo - Gold Edition available on March 20 exclusively at Walmart.

 Mario has always been golden in the minds of his fans. On March 20, Nintendo will launch the Super Mario amiibo—Gold Edition, a shiny gold-colored Mario figure that arrives on the same day as the Mario Party 10 game for the Wii Uconsole. The Super Mario amiibo—Gold Edition will be sold exclusively at 3,000 Walmart stores in the U.S. at launch at a retail price of $12.96. 

Super Mario amiibo - Gold Edition will be available on March 20 exclusively at Walmart 

Nintendo’s amiibo are interactive toys that come to life in compatible games in different ways. This new golden figure represents the third Mario amiibo. The other two Mario amiibo are:

• The original ‘fireball’ Mario from the Super Smash Bros. series.
• A new ‘wave’ Mario from the Super Mario series available on March 20, for a limited time bundled only with Mario Party 10.

The new gold-colored Mario amiibo is compatible with multiple games that support amiibo. For example, Mario Party 10 features a new amiibo Party mode that players can only access by tapping their compatible amiibo figures on the Wii U GamePad controller to customize them and bring them into the game as board pieces. Players can also save items to their amiibo, then use them strategically. Or players can train their amiibo to supercharge its stats and expand its abilities in Super Smash Bros. for Wii U or Super Smash Bros. for Nintendo 3DS. The full list of compatible games and amiibo can be found at http://www.nintendo.com/amiibo/compatibility.

For more information about amiibo, visit http://www.nintendo.com/amiibo.

Source: Nintendo press release