In Thai tradition, there is an astrological rule (which has influence from Hindu mythology) that assigns one particular color to each day of the week. The color assigned is based on the color of the God who protects the day. For example, the God of Sunday is Surya which has a red color. These colors of the day are the traditional Thai birthday colors. For example, King Bhumibol was born on Monday, so on his birthday (which was on December 5) the whole of Thailand was decorated in yellow color. Many Thai people believe that if they dress with the color synchronized to the respective day, it will bring good luck.
Once I knew this I started to notice these "color coded people" a lot, dressing accordingly to the color of the respective day. If you wear a yellow shirt on Monday, people will notice and might even comment on you wearing the "right" color. What a great concept - if you follow this tradition you never have to confront the awkward question of "what to wear today" after just having managed to crawl out of bed in the morning. But designers be aware: Our favorite color black is not considered a lucky color, at least not to the older generation. They reserve the black color for funerals and might even be offended if you wear black on a party. However, if you go to a party of the younger generation, black is trendy - just as anywhere else on the planet. Pheeew!