Gold purity is measured in karats. Each karat represents a 24th of the material being gold. This means, 24k gold is 100% pure gold, 18k gold is 75% gold, 14k gold is 58.3% gold, and 10k gold is 41.7% gold with the rest of the material being other metals in order to create the alloy. The purity also gives the gold different colors, durability, and weight. 24k gold will be the most pure gold color and it will also be the heaviest, but it is soft and not very good for everyday use. In contrast, 10k gold is much lighter in weight and color, but will also be the hardest.
Yellow gold has a nice warm, regular gold color to it. Yellow gold is very resistant to corrosion, rust, and tarnishing.
Rose gold has a wonderful pink hue to it that it gets from adding copper to the alloy. Rose gold does not fade or change color over time.
White gold is an alloy of gold that contains metals such as palladium, silver, or nickel in order to give it the silver-white color that it's known for. White gold is usually also plated with Rhodium to give the gold an even more white color.