According to one online dictionary, "yellow metal" refers to a brass that has more zinc and is stronger than alpha brass; used in making castings and hot-worked products.
Gold is the only metallic element which is yellow, it is often referred to as 'The Yellow Metal' especially in financial or commodity reports. 'Yellow metal' also refers to a brass alloy used in industry.
All metallic elements are silver coloured, except for two, namely gold which is yellow, and copper which is red.
Metal Alloys & Colours
Materials show colour because of their ability to handle different wavelengths of light in diiferent ways. These include absorption, reflection, and refraction. The effects usually depend on the crystal structure of the material. For more information, we suggest referring to an authoritive work on light as a department of physics.
Other Colours of Gold
In the jewellery industry, the expressions "white gold", "red gold", "pink gold", and "rose gold" are used, together with a few other colours. These are not colours of gold itself, but colours of gold alloys.
An alloy is a mixture of two or more metallic elements. By combining these in differing proportions, it is possible to produce "carat golds" with different colours.
Index of live spot gold price information on this website.
Investment Gold Glossary
In Gold We Trust!
Ingot We Trust! - Johnson Matthey 5 Tola Gold Bar