Highlight an equation within an align environment with color option
You can just add one more parameter to the macro. Below I have made the first parameter to specify the color -- it is optional and defaults to yellow if not provided as in the first example:
Notes:
- The main portion of this code is form Highlight an equation within an align environment, so please up vote that answer instead -- my addition here is just the addition of the first optional parameter.
Code:
\documentclass{article}
\usepackage{calc}
\usepackage{amsmath}
\usepackage{xcolor}
\newlength\dlf
\newcommand\alignedbox[3][yellow]{
% #1 = color (optional, defaults to yellow)
% #2 = before alignment
% #3 = after alignment
&
\begingroup
\settowidth\dlf{$\displaystyle #2$}
\addtolength\dlf{\fboxsep+\fboxrule}
\hspace{-\dlf}
\fcolorbox{red}{#1}{$\displaystyle #2 #3$}
\endgroup
}
\begin{document}
\begin{align*}
\alignedbox{a}{=b} & c &= d \\
c &= d & \alignedbox[magenta!20]{i}{=k} \\
e &= f & g &= h
\end{align*}
\end{document}
Another possibility is to exploit the hf-tikz
package.
A couple of examples:
\documentclass[11pt,a4paper]{article}
\usepackage{amsmath}
\usepackage[customcolors,shade]{hf-tikz}
\begin{document}
\begin{align*}
\tikzmarkin[fill=yellow]{first eq}a &= b\tikzmarkend{first eq} & c &= d \\
c &= d & i &= k \\
\tikzmarkin{second eq}e &= f\tikzmarkend{second eq} & \hfsetbordercolor{blue}\tikzmarkin[top color=white, bottom color=blue!20]{third eq}g &= h\tikzmarkend{third eq}
\end{align*}
\end{document}
which give the following result: