\begin{scope}[node distance=0.75cm]

\node (FGX) [color=blue,inner xsep=0.01cm, inner ysep=0.03cm] at (0, 0) {@};
\node (FG)  [color=blue,xshift=0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=FGX, left of=FGX]  {@};
\node (X)   [xshift=-0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=FGX, right of=FGX] {y};
\node (F)   [color=blue,xshift=0.25cm, inner xsep=0.04cm, inner ysep=0.05cm, below of=FG, left of=FG, xshift=2]   {f};
\node (G)   [xshift=-0.25cm, inner xsep=0.01cm, inner ysep=0.03cm, below of=FG, right of=FG, xshift=-2] {x};

\draw[->] (FGX) to (X);
\draw[->,color=blue] (FGX) to (FG);
\draw[->,color=blue] (FG)  to (F.north east);
\draw[->] (FG)  to (G.north west);

\end{scope}