Diagram with stacks

Question

So this is what I would like to have (please don't mind my awful paint skills):

And this is what I got out of tikz:

Using this code:

\documentclass{article}

\usepackage[english]{babel}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}

\begin{document}

\tikzstyle{depot}=[circle, draw, fill=red]
\tikzstyle{station}=[circle, draw, fill=green]
\tikzstyle{customer}=[circle, draw, fill=yellow]
\tikzstyle{line}=[draw, -latex']

\begin{tikzpicture}[node distance=2cm]
  \node[depot](s) {$s$};
  \node[station, right of=s](p1) {$p_1$};
  \node[rectangle, draw=black, right of=p1](c1) {\begin{tabular}{c} $c_1$\\\hline $d_1$\\\hline $d_2$ \\\hline $d_3$ \\\hline $\vdots$ \\\hline $d_{m(i)}$\end{tabular}};
  \node[station, right of=c1](p2) {$p_2$};
  \node[rectangle, draw=black, right of=p2](c2) {\begin{tabular}{c} $c_1$\\\hline $d_1$\\\hline $d_2$ \\\hline $d_3$ \\\hline $\vdots$ \\\hline $d_{m(i)}$\end{tabular}};
  \node[depot, right of=c2](t) {$t$};
\draw[thick, ->] (s) -- node[yshift=.2cm] {$t_{sp_1}$} (p1);
\draw[thick, ->] (p1) -- node[yshift=.2cm] {$t_{p_1c_1}$} (c1);
\draw[thick, ->] (c1) -- node[yshift=.2cm] {$t_{c_1p_2}$} (p2);
\draw[thick, ->] (p2) -- node[yshift=.2cm] {$t_{p_2c_2}$} (c2);
\draw[thick, ->] (c2) -- node[yshift=.2cm] {$t_{c_2t}$} (t);
\end{tikzpicture}

\end{document}

As I'm new to tikz, I'm not sure how to resolve the remaining issues:

1. The horizontal lines in the table have white space on both sides, and the table is too wide.
2. The arrows should point at specific entries in the table, not just to the middle of the table.
3. The table colors (color of top cell must be different from remaining cells). Btw, I'm open minded towards a prettier color scheme and a cleaner overall look :).
4. If possible, the rounded table top, but that's just bonus.

Any suggestions are highly appreciated.

Answer 1

Instead of tabulars, you can use a multipart rectangle (requires the shapes.multipart library (section 48.6 Shapes with Multiple Text Parts of the PGF manual)) for the stack-like shapes (this solves all your four requests); in the following code I also changed the old \tikzstyle for the newer \tikzset and changed the deprecated right of= syntax to right=of (with the positioning library):

\documentclass{article}
\usepackage[english]{babel}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows,shapes.multipart,positioning}

\definecolor{mygreen}{RGB}{0,146,63}
\definecolor{myred}{RGB}{218,37,28}
\definecolor{myblue}{RGB}{0,146,221}
\definecolor{mygray}{RGB}{186,179,213}

\tikzset{
depot/.style={
  circle,
  draw,
  fill=myred!80,
  text width=12pt,
  align=center},
station/.style={
  circle,
  draw,
  fill=mygreen,
  text width=0.75cm,
  align=center},
customer/.style={circle, draw, fill=yellow},
line/.style={draw, -latex'},
myrect/.style={
  rectangle split,
  rectangle split parts=5,
  draw,
  anchor=center,
  text width=0.8cm,
  align=center,
  rectangle split part fill={mygray!90}},
top/.style={
  draw,
  fill=myblue,
  rounded corners,
  text width=0.8cm,
  text depth=1.5ex,
  align=center
  }
}

% centered version of \vdots
\makeatletter
\DeclareRobustCommand{\rvdots}{%
  \vbox{
    \baselineskip4\p@\lineskiplimit\z@
    \kern-\p@
    \hbox{.}\hbox{.}\hbox{.}
  }}
\makeatother

\begin{document}

\begin{tikzpicture}[node distance=1.2cm]
\node[depot] (s) {$s$};
\node[station, right = of s] (p1) {$p_1$};
\node[top,above right= 1.8cm of p1] (t1) {$\mathstrut c_1$};
\node[myrect,below= -5pt of t1] (c1) 
  {$\mathstrut d_1$\nodepart{two}$\mathstrut d_2$
    \nodepart{three}$\mathstrut d_3$\nodepart{four}$\rvdots$
    \nodepart{five}$d_{m(i)}$};
\node[station, right = of c1] (p2) {$p_2$};
\node[top,above right= 1cm and 1.5cm of p2] (t2) {$\mathstrut c_1$};
\node[myrect, below= -5pt of t2] (c2) 
  {$\mathstrut d_1$\nodepart{two}$\mathstrut d_2$
    \nodepart{three}$\mathstrut d_3$\nodepart{four}$\rvdots$
    \nodepart{five}$d_{m(i)}$};
\node[depot, right = of c2](t) {$t$};

\draw[thick, ->] (s) -- node[above] {$t_{sp_1}$} (p1);
\draw[thick, ->] (p1) -- node[above,sloped] {$t_{p_1c_1}$} (c1.text west);
\draw[thick, ->] (c1.text east) -- node[above,sloped] {$t_{c_1p_2}$} (p2);
\draw[thick, ->] (p2) -- node[above,sloped] {$t_{p_2c_2}$} (c2.three west);
\draw[thick, ->] (c2.three east) -- node[above,sloped] {$t_{c_2t}$} (t);
\end{tikzpicture}

\end{document}

The trick to get rounded corners on top and sharp corners on bottom was to use a rectangular node with rounded corners for the top part, and then to superimpose appropriately a multipart rectangle with sharp corners for the remaining elements.

Instead of the standard \vdots I used the modified version \rvdots from the answer to How to vertically center the \vdots in this node?.