Why does a red object appears red under yellow light?

because its TOTO's favorite color

Answer: While author L. Frank Baum claims the book was written as a modern day faerie tale, both Baum and the books illustrator had been very actively involved in politics in the 1890's. The book was published in 1900 not more than four years after William Jennings Bryan delivered his famous "Cross of gold" speech at the 1896 Democratic National Convention in Chicago. The speech was in support of the Democratic parties push to take the U.S. dollar off of the "gold standard" and place it on a "silver standard". Of course, since the price of gold was all ready fixed to the price of silver because the dollar was silver, any notion of the U.S. truly being on a gold standard was convoluted at best. Many political interpretations of The Wizard of Oz suggest that "modern day faerie tale" was an allegory for the politics of the time. Indeed, much of Europe's faerie tales served as political allegories as well.

In a political context then, the Yellow brick road could mean the "gold standard" by which the Eastern "banking" cities believed was in the countries best interest, and in the book Dorothy was wearing silver slippers instead of the ruby slippers seen in the movie, and those silver slippers would then represent the silver standard advocated by William Jennings Bryan. Many believe, in fact, that the cowardly lion is a parallel to Bryan, while the scarecrow represents the plight of the American farmer and the tin man represents the plight of labor mechanized by a heartless industrial revolution. In fact, the line in Bryans oratory: "Having behind us the producing masses of this nation and the world, supported by the commercial interests, the laboring interests and the toilers everywhere, we will answer their demand for a gold standard by saying to them: You shall not press down upon the brow of labor this crown of thorns, you shall not crucify mankind upon a cross of gold."

It is the cowardly blustering lion Bryan who is looking for the courage to defend the poor dumb farmer and mechanized tin man without a heart, but they all are led down the Yellow Brick Road to the land of Oz where the American dream is offered by false prophets that hide behind curtains with pretense of magic and sorcery and yet, in the end all roads lead to Kansas, where one can find happiness with the comfort of home and family.