Complex sentence: 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 based on the color of the God who protects the day or Navagraha.
Split into simpler sentences: 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.