In Khmer and Thai traditions, there is an astrological rule (which has influence from Hindu mythology) that assigns color for each day of the week. The color is assigned based on the color of the God who protects the day or Navagraha. For example, the God of Sunday is Surya which has 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 throughout Thailand will be decorated with yellow color.