The basic clothing that the Buddha originally suggested for a bhikkhu was made from discarded cloth (‘rags’) sewn together and dyed.
After sewing the pieces together, they were just large rectangular pieces of cloth worn wraparound style.
In the beginning, it seems that there were two robes: a sarong skirt-like robe (antaravaasaka) tied with a belt, and a robe to cover the upper part of the body (uttaraasa”nga).
When the cold weather required more protection, the Buddha allowed a third robe, which was a double-thickness outer robe (sa”nghaa.ti).
For most Buddhist schools, including those whose monks wear red robes, there is no special significance to this color.
Originally monks dressed in ochre/saffron/yellowish robes, but there were some variation as the actual shade depends on the pigment used. As Buddhism spread to different regions of the world, pigments extracted from local products were used to dye the robes, producing different hues towards the maroon, brownish or plain red.
In some locations, such as Japan and Korea, robes eventually became gray, black and even bright blue.
The most common colours are seen in these countries
🇲🇲Burma / Myanmar and 🇦🇬Tibet — Red
🇹🇭Thailand 🇭🇹Cambodia and 🇱🇦Laos- orange
🇱🇰Sri Lanka- Yellowish/Orangish
🇨🇳China and 🇰🇷Korea — Grey / Light Blue
🇯🇵Japan- Black
