Red represents courage and the physical human body, while white represents purity and the spiritual soul. These are traditional Austronesian colors.
History
The 'Sang Saka Merah Putih' was officially adopted on August 17, 1945, when Indonesia declared independence from the Netherlands. The design dates back to the 13th-century Majapahit Empire.
Construction
A 2:3 ratio. Two equal horizontal bands of red (top) and white (bottom).