颜色版

http://colorbrewer2.org/#type=sequential&scheme=BuGn&n=3

https://stackoverflow.com/questions/33596491/extract-matplotlib-colormap-in-hex-format

from pylab import *

cmap = cm.get_cmap('seismic', 5)    # PiYG

for i in range(cmap.N):
    rgb = cmap(i)[:3] # will return rgba, we take only first 3 so we get rgb
    print(matplotlib.colors.rgb2hex(rgb))