24 karat gold has the natural warm colour of pure gold and its colour cannot be changed without changing the purity to less than 24 k. Other colours of gold can be made by changing the composition of the alloy in the making of the jewellery.

Pink or Rose gold - Pink gold is made by adding more copper in the alloy composition of the gold
Green Gold – Gold is given a green colour by adding more of zinc and silver
White Gold – the white colour of gold is achieved by adding nickel or palladium
A surface colour can also be given to gold articles by electro-plating. However this can only be a surface finish and will be worn off over a period of time.