According to ancient customs in Thailand, there is an astrological rule (which has influence from Hindu mythology) that assigns a color to each day of the week based on the color of the God who protects the day or Navagraha.[1] For example, the God of Sunday is Surya who has the color red. These colors of the day are traditional Thai birthday colors. As King Bhumibol and his son were born on Mondays, Thailand is decorated with yellow on their birthdays. Thai people often wear clothes corresponding to the color of the day.
| Sunday | วันอาทิตย์ | Red | Surya | |
| Monday | วันจันทร์ | Yellow or Cream | Chandra | |
| Tuesday | วันอังคาร | Pink | Mangala | |
| Wednesday | วันพุธ | Green | Budha | |
| Thursday | วันพฤหัสบดี | Orange | Brihaspati | |
| Friday | วันศุกร์ | Light Blue | Shukra | |
| Saturday | วันเสาร์ | Purple | Shani | |
In cultures outside of Thailand, there is also the concept of colors of the seven days, but the colors are not fixed. There are also some cultures that represent the colors of the seven days in the spectral order of the rainbow, such as the lighting ceremony of Taipei 101.[4]