Yellow gold is naturally warm in color and is the normal color of gold. Depending on the karat (amount of pure gold) in the ring, it will vary from a light yellowish-gold color to a darker more pure gold color.
Rose gold has a pink hue to it, similar to copper. It is a gold alloy that gets its color by adding copper to the gold. Higher karat rose gold gets a warmer color to it and can start to appear a little less pink due to having more natural gold in it.
White gold has a silver-white color. It gets its color from mixing metals such as palladium, silver, and nickel into it to create the white gold alloy. It is also plated with rhodium to give it an even more of a white color. White gold doesn't vary much in color based on karat count.