Hi!
I'd like to add highlight to my Maths formulas.
I've found that "\colorbox{aqua}{...}" works great but it doesn't like when there are exponent or fraction:

This formula with exponent doesn't work:
$\colorbox{aqua}{E = mc^2}$

Error:

KaTeX parse error: Expected 'EOF', got '^' at position 23: …ox{aqua}{E = mc^̲2}

And this formula with fraction inside neither:
$\colorbox{aqua}{U = -\frac{G m_1 m_2}{r} }$ gives the error:

KaTeX parse error: Can't use function '\frac' in text mode at position 17: …colorbox{aqua}{\̲f̲r̲a̲c̲{

How can I find a way to highlight my Maths formulas when they contain power exponent or fraction?
Thanks a lot in advance!