We all know that Zevulun was engaged in commerce and trade. (Zevulun also supported the tribe of Yissachar who were primarily engaged in Torah studies.) Being that Zevulun were the" businessmen" of the 12 tribes, their honesty had to be impeccable. The color white represents purity .Zevulun's business practices had to be pure and free of any financial improprieties. A person who truly believes in G-d will never be tempted to steal or to cheat in order to earn a living. A man of faith knows that G-d is in control of how much he will earn, cheating and stealing is therefore unnecessary. Therefore, white is an appropriate color for the tribe of Zevulun. Zevulun's faith (BITACHON) in G-d had to be pure (white) so that his every day business practices could in essence represent his inner faith in Hashem. When Zevulun conducted business he also represented the entire Jewish nation , and especially G-d. We all need to analyze our own business practices to see how we might be viewed by others.Do people want to do business with us because of our honesty, or do they try to avoid us? Do we appear before people as a "white" gem full of faith in Hashem, or not? Some misinformed people might look down upon Zevulun's purpose, yet the Torah makes the tribe an example to all of us as represented by the white gem as to how honest we ought to be. Zevulun represented true faith in Hashem. We must learn from Zevulun's example. Have a good Shabbos.............