hmag = np.array(hmag)
jmag = np.array(jmah)
colorjh = jmag - hmag
idx = ((colorjh > 0) & (colorjh < 1) & (hmag > 10) & (hmag < 13)).nonzero()[0]
plt.scatter(colorjh[idx], hmag[idx], c='g', s=1, alpha=0.05)
How to slice up a numpy array with inequalities?