Color of the day is based on ancient astrological mythology that each day is assigned a color based on the color of the God who protects that day (influence from Hindu mythology). Wearing a respective auspicious color for each day is believed to bring luck and success to self. This custom is well known in Thailand and it is common to see people wear auspicious color for the day.
Day - God of the day - Corresponding planet
Monday
Color: Yellow
God of the day: Chandra
Corresponding planet: Moon
Tuesday
Color: Pink
God of the day: Mangala
Corresponding planet: Mars
Wednesday
Color: Green
God of the day: Budha
Corresponding planet: Mercury
Thursday
Color: Orange
God of the day: Brihaspati
Corresponding planet: Jupiter
Friday
Color: Light Blue
God of the day: Shukra
Corresponding planet: Venus
Saturday
Color: Purple
God of the day: Shani
Corresponding planet: Saturn
Sunday
Color: Red
God of the day: Surya
Corresponding planet: Sun