import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-4, 4, 180)
y = np.linspace(-4, 4, 180)
X, Y = np.meshgrid(x, y)
Z = np.exp(-(X**2 + Y**2) / 4) * np.cos(X * 2) * np.sin(Y * 2)

fig, ax = plt.subplots()
ax.pcolormesh(X, Y, Z, cmap="jet")
ax.set_title("A misleading 'jet' colormap")
ax.set_xlabel("x")
ax.set_ylabel("y")