The yellow parts of the culm are sometimes tinted with a rose highlight in bright sun. e all aureas, Koi is a drought tolerant and dense bamboo which makes an excellent thick screen.One of the most interesting color variations, the culms are green at first becoming yellow with a green sulcus after a few months. The yellow parts of the culm are sometimes tinted with a rose highlight in bright sun. Koi is used to make umbrella handles and canes because of the odd way that that several short internodes form near the base of the culms. This plant makes an excellent privacy screen. This colorful form has the same growth habit as the original plant, though usually not as fast spreading.