The Lord Buddha gave this reflection about why a monk wears a robe:

Properly considering the robe, I use it: simply to ward off cold, to ward off heat, to ward off the touch of flies, mosquitoes, simply for the purpose of covering the parts of the body which cause shame.

In the Lord Buddha’s time, 2,500 years ago, clothing was made without complex machinery. (Although simple ‘sewing-frames’ are mentioned in the texts, which the monks would have used at robe-making – Kathina – time.) So the pattern of the robe is very simple and designed so that it can be made up out of patches of cloth, for discarded rags were often used after washing and dyeing.

This “yellow robe” is considered the banner of the arahant and emblem of Buddhism. For the ordinary monks it is a privilege to be able to wear this robe, continuing the tradition and practicing to be worthy of it.

There are rules as to the robes’ size, color, how they are sewn, type of cloth used, etc.

The color of the robes depends on the dye used. Until very recently, this would have been natural vegetable dye found in the jungle from roots or trees.

Nowadays chemical dyes are more used and sometimes give that more vivid orange color that one sees in Bangkok.

The color white is used by Buddhist devotees to show their commitment to keeping the Precepts — usually the Eight Precepts — on Observance Days. (White robes are also worn by the anagarika, or postulant before he becomes a monk.)

Learn more about the Theravadin Buddhist Monk’s Rules here:

The Bhikkhus’ Rules – Guide for Laypeople