# Multiline equation environment coloring changes from one line to the other?

Does there exist a multiline equation environment which automatically shows the changes from one line to the other?

I am thinking of an environment that would take inputs like

       E[d] & = \sum_{d=0}^{\infty} \frac{\lambda^d}{d!} d e^{-\lambda}\\
& = \sum_{d=1}^{\infty} \frac{\lambda^d}{d!} d e^{-\lambda}\\
& = \lambda \sum_{d=1}^{\infty} \frac{\lambda^{d-1}}{d!} d e^{-\lambda}\\
& = \lambda \sum_{d=1}^{\infty} \frac{\lambda^{d-1}}{(d-1)!} e^{-\lambda}\\
& = \lambda \sum_{d=0}^{\infty} \frac{\lambda^{d}}{(d)!} e^{-\lambda}\\
& = \lambda\\


and output something like

Ideally, the math in the output should not be distorted as in the above example (e.g. the (d-1) in exponent should still have exponent size).

Edit : I am looking for an environment that would produce this kind of output automatically, without having to manually identify the changes and tag them with a certain color (which is what I did using colorbox to generate the example).

One possibility is use colorbox from package xcolor

\documentclass{article}
\usepackage{mathtools}
\usepackage[dvipsnames]{xcolor}
\newcommand{\shadow}[1]{\scriptsize\colorbox{orange!40}{$#1$}}
\newcommand{\shadowf}[1]{\footnotesize\colorbox{orange!40}{$#1$}}
\newcommand{\shadown}[1]{\colorbox{orange!40}{$#1$}}

\usepackage[active,displaymath,tightpage]{preview}
\setlength\PreviewBorder{5pt}%

\begin{document}
\begin{align*}
E[d] & = \sum_{d=0}^{\infty} \frac{\lambda^d}{d!} d e^{-\lambda}\\
& = \sum_{d=\shadow{1}}^{\infty} \frac{\lambda^d}{d!} d e^{-\lambda}\\
& = \lambda \sum_{d=1}^{\infty} \frac{\lambda^{\shadowf{d-1}}}{d!} d e^{-\lambda}\\