Gold is considered a pure material since it never gets rust and in that, matches the pure lifestyle of a Buddhism monk, therefore one will observe the gold or gold color in use is overwhelm for the Buddhism temples.
The monk’s robe would be ideal in gold color but it might get mugged easily so instead the monk wears a color to be close to gold. In the Pāli Canon (Pāli Tradition), the robe dye is allowed to be obtained from six kinds of substances: root of tubers, plants, bark, leaves, flowers and fruits. They should be boiled in water for a long time to get the dun dye. And Saffron and ochre are the most prevalent colors today.