The two most common causes for bamboo turning yellow include watering the plant with tap water with high levels of fluoride and exposing it to too much direct sunlight. Bamboo plants may also turn yellow due to the overuse of fertilizer or injury.
To properly water a bamboo plant, use bottled or filtered water. If you cannot afford bottled water for the plant, allow tap water to sit for 24 hours before using it to water the plant. If the plant sits in direct sunlight for too long, it can get sunburn and turn yellow. Taking it away from the sun often helps turn it back to a normal color.