I have quite a few culms of bamboo that have been around for a while, not pre embargo but pre Lewinsky anyway. Many of the culms have some greenish areas and occasionally some grey areas in the nodes after you prep them. All you need to do is expose the culm or the strips to direct sun for a few days and the green or grey will go away. My culms are stored indoors in a garage so they have not had much sun time. So don't worry about the color variations just set them in the sun.
I am a cane rod builder and co-founder of Canadian Cane