Fixed another review comment and extended explanation

Author: oscargus

doc/users/next_whats_new/color_support_for_math_to_image.rst

@@ -1,9 +1,9 @@
 ``math_to_image`` now has a *color* keyword argument
 --------------------------------------------------------
 
-To easily support external libraries that rely on the rendering of Matplotlib
-to generate figures, a *color* keyword argument was added to
-``math_to_image``.
+To easily support external libraries that rely on the MathText rendering of
+Matplotlib to generate equation images, a *color* keyword argument was added
+to`~matplotlib.mathtext.math_to_image`.
 
 .. code-block:: python