# use masked arrays to plot a line with different colors by y-value from numpy import logical_or, arange, sin, pi from numpy import ma from matplotlib.pyplot import plot, show t = arange(0.0, 2.0, 0.01) s = sin(2*pi*t) upper = 0.77 lower = -0.77 supper = ma.masked_where(s < upper, s) slower = ma.masked_where(s > lower, s) smiddle = ma.masked_where(logical_or(s<lower, s>upper), s) plot(t, slower, 'r', t, smiddle, 'b', t, supper, 'g') show()