Gold comes in many shapes, sizes, and also colors!!! The gold many people know and love is actually a mixture of different metals. Gold from the ground comes as 24 karat and has a darker yellow/orange color.
A majority of the Gold in the United States is a mixture of Gold, Silver, Copper, Nickel and so on. Where gold is found, a lot of times there will be silver and copper elements in the soil (probably were drinking buddies in college). In the US, gold can not be diluted to less than 10 karat in the US in order for it to be called gold. 10/24 = .417 or 41.7% gold. And not all alloy mixtures on the same and some manufacturers use more of 1 alloy to get a desired color. White gold has a higher mixture of Silver and Nickel in it compared to yellow gold. And rose gold with a higher mixture of copper in it to give it that red effect.
The mixture of alloys used will depend on what the product is. Example, casting alloy used for charms and rings have a different profile than rolling alloy that is used for chains and bracelets. Even though two chains can both be 14 karat, the manufacturers can use different alloys which sometimes gives the chains different colors between the two.
So even though a chain is 14 karat gold, they might look different depending on the alloys the manufacturers used. The chains and merchandise we like to bring for yellow gold tends to be on the lighter side because it gives a cleaner looking shine. It's all about style ;)