I wish to replicate the image in this post. However I can't do any of it except the basic stuff that my code does. Thanks for any help.
The exact coloring doesn't matter. Also I don't actually want those black lines around the coloring. Perhaps a darker blue line around the light blue coloring and a darker green line around the light green coloring.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix,fit,backgrounds,calc}
\begin{document}
\begin{tikzpicture}[>=stealth,sloped]
\matrix (tree) [%
matrix of nodes,
minimum size=1cm,
column sep=3.5cm,
row sep=0.6cm,
]
{
& |(top-left)| & |(top-right)| & $ $ \\
& & $_0S_{2\Delta t}$ & \\
& $_0S_{\Delta t}$ & & $ $ \\
$_0S_0$ & & $_1S_{2\Delta t}$ & \\
& $_1S_{\Delta t}$ & & $ $ \\
& & $_2S_{2\Delta t}$ & \\
& |(bottom-left)| & |(bottom-right)| & $ $ \\
};
\draw[->] (tree-4-1) -- (tree-3-2) node [midway,above] {$p$};
\draw[->] (tree-4-1) -- (tree-5-2) node [midway,below] {$1-p$};
\draw[->] (tree-3-2) -- (tree-2-3) node [midway,above](a) {};
\draw[->] (tree-3-2) -- (tree-4-3) node [midway,below] {};
\draw[->] (tree-5-2) -- (tree-4-3) node [midway,above] {};
\draw[->] (tree-5-2) -- (tree-6-3) node [midway,below] {};
\draw[->,dashed,shorten >= 17mm] (tree-2-3) -- (tree-1-4) node [midway,above] {};
\draw[->,dashed,shorten >= 17mm] (tree-2-3) -- (tree-3-4) node [midway,below] {};
\draw[->,dashed,shorten >= 17mm] (tree-4-3) -- (tree-3-4) node [midway,above] {};
\draw[->,dashed,shorten >= 17mm] (tree-4-3) -- (tree-5-4) node [midway,below] {};
\draw[->,dashed,shorten >= 17mm] (tree-6-3) -- (tree-5-4) node [midway,above] {};
\draw[->,dashed,shorten >= 17mm] (tree-6-3) -- (tree-7-4) node [midway,below] {};
% t-line
\draw[dashed] ($(top-left.north)!.5!(top-right.north)$) -- ($(bottom-left.south)!.5!(bottom-right.south)$);
\node at ($(bottom-left.south)!.5!(bottom-right.south)-(0,1em)$) {$\tau$};
\end{tikzpicture}
\end{document}


