The answer given to the above question by Ayatollah Hadavi Tehrani (may Allah grant him long life) is as under:
It is haram for men to use any kind of gold ornaments irrespective of whether they are in the form of a gold ring or a necklace or a gold-plated watch wrist. If white gold is the same conventional white gold which has the same value of the yellow gold, it is in reality the white gold which has been blended with white metal to get that white hue. It is therefore haram for men to wear it. However, if white gold refers to platinum which is dearer than gold, it is permissible for men to wear it.