Repository: ManimCommunity/manim
File: manim/mobject/svg/tex_mobject.py (Python)

Code before:
    :save_last_frame:

    class IncorrectLaTeXSubstringColoring(Scene):
        def construct(self):
            equation = MathTex(
                "e^x = x^0 + x^1 + \\frac{1}{2} x^2 + \\frac{1}{6} x^3 + \\cdots + \\frac{1}{n!} x^n + \\cdots"
                )
            xs = equation.get_parts_by_tex("x")
            xs.set_color_by_tex(YELLOW)
            self.add(equation)

As you can see, this colors the entire equation yellow, contrary to what may be expected. To color only ``x`` yellow, we have to do the following:

.. manim:: CorrectLaTeXSubstringColoring
    :save_last_frame:

    class CorrectLaTeXSubstringColoring(Scene):
        def construct(self):
            equation = MathTex(
                "e^x = x^0 + x^1 + \\frac{1}{2} x^2 + \\frac{1}{6} x^3 + \\cdots + \\frac{1}{n!} x^n + \\cdots", substrings_to_isolate="x"
                )
            xs = equation.get_parts_by_tex("x")
            xs.set_color(YELLOW)
            self.add(equation)

By setting ``substring_to_isolate`` to ``x``, we split up the :class:`~.MathTex` into substrings automatically and isolate ``x`` components into individual substrings. :func:`~.set_color_by_tex`: can then be used to achieve the desired result.

LaTeX Maths Fonts - The Template Library
++++++++++++++++++++++++++++++++++++++++
Changing fonts in LaTeX when typesetting mathematical formulae is a little bit more tricky than
with regular text. It requires changing the template that is used to compile the tex code.
Manim comes with a collection of :class:`~.TexFontTemplates` ready for you to use. These templates will all work
in maths mode:

.. manim:: LaTeXMathFonts
    :save_last_frame:

    class LaTeXMathFonts(Scene):
        def construct(self):
            tex = Tex(r'$x^2 + y^2 = z^2$', tex_template=TexFontTemplates.french_cursive).scale(3)
            self.add(tex)

Manim also has a :class:`~.TexTemplateLibrary` containing the TeX templates used by 3Blue1Brown. One example
is the ctex template, used for typesetting Chinese. For this to work, the ctex LaTeX package
must be installed on your system. Furthermore, if you are only typesetting Text, you probably do not
need :class:`~.Tex` at all, and should use :class:`~.Text` or :class:`~.PangoText` instead.

.. manim:: LaTeXTemplateLibrary
    :save_last_frame:

    class LaTeXTemplateLibrary(Scene):

Review comment (suggestion):
Minor rewording (I don't like sentences starting with functions), and removed a superfluous colon.

```suggestion
By setting ``substring_to_isolate`` to ``x``, we split up the :class:`~.MathTex` into substrings
automatically and isolate ``x`` components into individual substrings. Only then can :meth:`~.set_color_by_tex` be used to achieve the desired result.
```

Code after:
    :save_last_frame:

    class IncorrectLaTeXSubstringColoring(Scene):
        def construct(self):
            equation = MathTex(
                r"e^x = x^0 + x^1 + \frac{1}{2} x^2 + \frac{1}{6} x^3 + \cdots + \frac{1}{n!} x^n + \cdots"
            )
            equation.set_color_by_tex("x", YELLOW)
            self.add(equation)

As you can see, this colors the entire equation yellow, contrary to what may be expected. To color only ``x`` yellow, we have to do the following:

.. manim:: CorrectLaTeXSubstringColoring
    :save_last_frame:

    class CorrectLaTeXSubstringColoring(Scene):
        def construct(self):
            equation = MathTex(
                r"e^x = x^0 + x^1 + \frac{1}{2} x^2 + \frac{1}{6} x^3 + \cdots + \frac{1}{n!} x^n + \cdots",
                substrings_to_isolate="x"
            )
            equation.set_color_by_tex("x", YELLOW)
            self.add(equation)

By setting ``substring_to_isolate`` to ``x``, we split up the :class:`~.MathTex` into substrings
automatically and isolate ``x`` components into individual substrings. Only then can :meth:`~.set_color_by_tex` be used to achieve the desired result.

LaTeX Maths Fonts - The Template Library
++++++++++++++++++++++++++++++++++++++++
Changing fonts in LaTeX when typesetting mathematical formulae is a little bit more tricky than
with regular text. It requires changing the template that is used to compile the tex code.
Manim comes with a collection of :class:`~.TexFontTemplates` ready for you to use. These templates will all work
in maths mode:

.. manim:: LaTeXMathFonts
    :save_last_frame:

    class LaTeXMathFonts(Scene):
        def construct(self):
            tex = Tex(r'$x^2 + y^2 = z^2$', tex_template=TexFontTemplates.french_cursive).scale(3)
            self.add(tex)

Manim also has a :class:`~.TexTemplateLibrary` containing the TeX templates used by 3Blue1Brown. One example
is the ctex template, used for typesetting Chinese. For this to work, the ctex LaTeX package
must be installed on your system. Furthermore, if you are only typesetting Text, you probably do not
need :class:`~.Tex` at all, and should use :class:`~.Text` or :class:`~.PangoText` instead.

.. manim:: LaTeXTemplateLibrary
    :save_last_frame:

    class LaTeXTemplateLibrary(Scene):