colormap_bw_wr.py

import numpy as np 
import matplotlib.pyplot as plt 

from matplotlib.colors import LinearSegmentedColormap

clist=[(1,1,1),(1,0,0)]
cm = LinearSegmentedColormap.from_list('wr',clist)
plt.register_cmap(cmap=cm)

clist=[(0,0,1),(1,1,1)]
cm = LinearSegmentedColormap.from_list('bw',clist)
plt.register_cmap(cmap=cm)

h = 0.01
lm = [-2, 2]
x = np.arange(lm[0],lm[1]+h,h)
y = np.arange(lm[0],lm[1]+h,h)
xx,yy=np.meshgrid(x,y)
zz = xx+yy

plt.close('all')
plt.figure()

plt.subplot(1,3,1)
plt.imshow(zz,cmap='bw')
plt.title('bw')
plt.subplot(1,3,2)
plt.imshow(zz,cmap='bwr')
plt.title('bwr')
plt.subplot(1,3,3)
plt.imshow(zz,cmap='wr')
plt.title('wr')
plt.tight_layout()

plt.savefig('bw_wr.png')