Red gold contains, as you can guess by now, mostly copper. This is a very basic explanation of gold alloys. It should help you to understand the terms 18 karat, or 583 gold, and the colors. In reality, there are great variations in the alloy metals. Silver, for example, is often replaced with nickel and palladium for white gold.
Titanium is added to alloys, and so on.
It would be too much for this presentation to go into more detail. More important for you, the jewelry customer, is to understand how these terms influence the price. One Troy ounce is 31.1 grams. As you can see, there is not too big a difference for us, the jewelry makers. The difference between the 18K and 14K ring in this example is only eight dollars.