There are elephants which are termed white and these were an emblem of royalty in south-east Asia, in that kings sought them. The present King of Thailand, Rama IX, has a number of them. However, they are not actually white. They are, in fact, of a pink or brown color. As they are albinos, this has probably led to the term "white elephant" being applied to them.
Pure white elephants occur in oriental mythology and religion. The Hindu god Indra is said to ride one. Buddha's mother is said to have dreamed of one before he was born.
The showman P.T. Barnum wished to exhibit a white elephant. Finding they were in reality pink, he obtained a normal elephant and whitewashed it, no doubt fooling a gullible public.