Change the font in a Keynote equation

The built-in equation editor in Pages, Keynote, and Numbers is a [La]TeX and MathML translator. It is not a [La]TeX engine, so it prohibits one from including TeX packages (e.g. fontspec) that would allow you to use any installed font you choose.

About LaTeX and MathML support in Pages, Numbers, Keynote and iBooks Author. There is a direct link on that page to the blahtex PDF manual, whose font commands appear below:

\matchsf{e = mc^2}

\mathbf{e = mc^2}

\mathit{e = mc^2}

\color{BlueViolet}\mathtt{e = mc^2}

If you are typing in any font family known to Keynote, and then enter the equation editor, you are restricted to the limited example font faces that are illustrated in my preceding post, and which I explained in the first paragraph of that post.

Once you insert the equation, the continuance of typing after the equation will remain in the same font face as preceded the equation. However, because the equation is now a document object, and not actually text, you cannot change its font face to match that of its surrounding text.

I think what the original poster is asking is how to change the Keynote math font so it matches the fonts used in Keynote, not the fonts used in LaTeX. For example, for some reason, my Keynote is typesetting equations in an upright, sans serif font which does not match the rest of the document (which is in Palatino). This means that variables, which should be typeset in italics automatically are still upright. In this context, the answer given is not really an answer and is worth asking again:

How do you change in the math font in Keynote?