\begin{tikzpicture}[
      plant/.style = {
        draw, thick,
        minimum width = 1cm,
        minimum height = 1cm,
      },
      arrow/.style = {
        -latex, thick,
      },
    ]
  \matrix [row sep = 4mm, nodes={plant}] {
    \node [fill=red!10] (U) {$\Delta$}; \\
    \node [fill=blue!10] (G) {$G$}; \\ 
    \node [fill=green!10] (K) {$K$}; \\
  };

  \coordinate (Uz) at (U.west);
  \coordinate (Uv) at (U.east);

  \coordinate (Gz) at ($(G.north west) - (0, 2mm)$);
  \coordinate (Ge) at (G.west);
  \coordinate (Gy) at ($(G.south west) + (0, 2mm)$);

  \coordinate (Gv) at ($(G.north east) - (0, 2mm)$);
  \coordinate (Gw) at (G.east);
  \coordinate (Gu) at ($(G.south east) + (0, 2mm)$);
  
  \coordinate (Ky) at (K.west);
  \coordinate (Ku) at (K.east);

  \begin{scope}[arrow]
    \draw (Gz) -- ++(-1cm, 0) |- (Uz) node[left, pos=.25] {$z$};
    \draw (Ge) -- ++(-1cm, 0) -- ++(-5mm, 0) node[left] {$e$};
    \draw (Gy) -- ++(-1cm, 0) |- (Ky) node[left, pos=.25] {$y$};
    
    \draw (Uv) -- ++(1cm, 0) |- (Gv) node[right, pos=.25] {$v$};
    \draw (Gw) ++(15mm, 0) node[right] {$w$} -- (Gw);
    \draw (Ku) -- ++(1cm, 0) |- (Gu) node[right, pos=.25] {$u$};
  \end{scope}
\end{tikzpicture}