There is no "White Gold" in Engagement rings or earrings.

Unless you use the banned Nickel or the expensive Palladium alloys. “White gold” is actually yellowish Alloy that was dipped in the chrome-look Rhodium bath to

cover it (see photos). This is a thin cover
Called “Flash cover” and it is only about 0.002 mm.
These jewels need maintenance once or twice a year depending on the wearing conditions.
It is a common procedure and takes 15 minutes and can be applied on any other metals that require the removal of starches and dirt!

Gold ring after Rhodium dipping
18k “White” Gold, rough metal, not covered.

Rhodium dipped engagement ring

18k Gold ring after finish and Rhodium dipping.

Pure gold is too soft to hold valuables like Diamonds with claws (prongs) therefore the Gold Alloys were invented. 58.5% pure gold in any alloy will be called 14k Gold, 75% of pure Gold is 18k Gold, 24k is pure gold, 0.
Since Gold is a yellow metal “18k White gold” is an alloy of Gold (75%) and Nickel (8%) or Gold (75%) and Palladium (15%).

10 to 15% of women are allergic to Nickel released to their skin while wearing a jewel. This will result in different skin rash levels.

Metal prices as of 13th April 2010

Pure Platinum US$ 55 per Gram.
Pure Gold US$ 37 per Gram.
Pure Palladium US$ 16.4 per Gram.
Nickel US$ 0.025 per Gram !!!

It is clearly seen that using Palladium to make the alloy white will significantly increase the price and put it close to Platinum price.
The use of Nickel is banned by countries like Switzerland and controlled by regulations in the EU community; there is yet any Nickel use regulation in the USA.
European regulations limit the amount of nickel that could be released from any item which is intended to come into prolonged and direct contact with the skin.The regulations entitled “The Dangerous Substances and Preparations (Nickel) (Safety) Regulations 2005” clearly require that any finding component that pierces the skin may not release more than .2 micrograms of nickel per cubic centimeter per week, and that no other jewelry component release no more than .5 micrograms of nickel per cubic centimeter per week.
Nickel exposure is tested under BS EN12472 and BS EN 1811:1999. The first of these separate tests replicates two years of wear under normal use, and the second tests for subsequent exposure to nickel.
We at use only “Nickel free” metal alloys as required by the EU regulations.