In so far as red gold acted in the same way as gold for jewellery and industrial uses, it would probably decrease the value of gold to some proportion, and set a base level on this red gold production. But this is like asking why diamonds are valuable, or designer clothes, or expensive watches. In many cases, it's a combination of marketing, status display effects (ostentatious useless consumption), artificial restriction on supply, and market fixing (e.g. arranging to buy watches on secondary markets at headline prices for PR purposes). They too are confidence games, and if the confidence goes due to a bad association with the brand, the price will fall through the floor. All that is left is productive uses like industry.