There is no such thing as red, pink or rose gold!
There are however gold alloys which appear rose, red, or pink.
When jewellers speak of coloured gold, they mean coloured gold alloys.

Gold Alloys

Gold itself is a yellow metallic element but, in its pure form, it is too soft to be used for general jewellery purposes, although there are some cultures which do wear pure gold jewellery, it would need to be heavily made and carefully used. The yellow colour of gold is caused by gold absorbing violet and blue light, but reflecting yellow and red light.

It is usual for gold to be mixed with other metals to produce an alloy, which is simply a mixture of two or more metals. Throughout history, most people have preferred the colour of gold jewellery to remain close to that of pure gold itself, and so most jewellery has historically been made using yellow gold alloys. Most gold alloys are a mixture of gold, copper and silver. these three metals have a great metallurgical affinity for each other. Small amounts of other materials are also added to provide special characteristics.
Nickel, zinc, and palladium are common constituents of white gold alloys.

Rose, Red and Pink Gold Alloys

It is very simple to produce a gold alloy with a reddish colouration. All that is needed is to increase the proportion of copper in the mixture. To maintain the correct proportion of gold in the alloy, this usually means decreasing the silver content. In the past, many goldsmiths have reduced the silver content and increased the copper content to save cost, as copper is less expensive than silver.
We encounter many people who believe that red gold is old gold, and vice versa; also that old gold is better than new gold. Neither of these beliefs are accurate.
Certainly, some old gold was reddish, and some old gold is better than some new gold, but not necessarily.

So what is the difference between red, rose, and pink golds?
Only the name. All three are basically the same, although "rose" gold has a certain romantic marketing ring to it! Many goldsmiths use all three expressions interchangeably, as I do. However, the words rose and pink carry softer overtones, so I tend to use red to denote a deeper red, and pink or rose to denote a softer, warmer colour.

It is not often realised that there are only two metallic elements which are not silvery coloured. Gold is yellow, and copper is red. By adjusting the proportions of these metals, gold, silver and copper, it is possible to vary the colour from very pale yellow, usually called "green" gold, to a deep red, or to a deep gold.

You may wish to visit some of our other pages:-
Allergies to Gold Jewellery
Gold Alloys by Weight & Volume
Hardness & Durability of Gold Alloys