Unable to render different colors for specific characters within a LaTeX string

I would like to change the color of a substring within a LaTeX string for a MatPlotLib plot title. The code below gives no errors or warning; but, does not render the color specified.

# -*- coding: utf-8 -*-
import numpy as np
import matplotlib
matplotlib.use("WXAgg")
import matplotlib.pyplot as plt
plt.rc('text', usetex=True)
plt.rc('text.latex', preamble = r'\usepackage{xcolor}')

N = 50
x = np.random.rand(N)
y = np.random.rand(N)

fig, ax = plt.subplots()
ax.scatter(x, np.cos(x), color = 'blue', marker = "+", s=47.5)
ax.set_title(r'$\color{red}{X}X$')
#ax.set_title(r"\textcolor{red}{X} $\color{red}{X}$") # does not work either

plt.show()

How can I render the first X with the color red?

--V

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