Is it a condition that the ihram garment for men be white in color, and what is the wisdom behind that?

The Sunnah for someone intending to perform Hajj or 'Umrah is to wear two white sheets (rada'ayn), because white garments are among the best of clothes, as the Prophet (peace and blessings be upon him) said: "Wear white garments, for they are purer and better, and shroud your dead in them." This is also because cleanliness is beloved in clothes just as it is in the body.