\documentclass[tikz]{standalone}


\begin{document}

\begin{tikzpicture}
	\fill[red!20!yellow] (0,0) rectangle (5,5);
	\fill[red!30!yellow] (1,1) rectangle (5,5);
	%\fill[red!20!yellow] (1,1) rectangle (2,2);
	\fill[red!40!yellow] (2,2) rectangle (5,5);
	\fill[red!60!yellow] (3,3) rectangle (5,5);
	\fill[red!80!yellow] (4,4) rectangle (5,5);
	\draw[step=1cm,gray,very thin] (0,0) grid (5,5);
	\node[rotate=-90] at (-0.1,0.5) {\tiny 1};
	\node[rotate=-90] at (-0.2,2.5) {\tiny \bfseries Y-axis};
	\node[rotate=-90] at (-0.1,4.5) {\tiny 5};
	\node[] at (0.5,-0.1) {\tiny 1};
	\node[] at (2.5,-0.2) {\tiny \bfseries X-axis};
	\node[] at (4.5,-0.1) {\tiny 5};

	\shade[inner color=green!20!white, outer color=green!40!black] (1.5,2.5) circle (0.3cm);"
	\shade[inner color=green!20!white, outer color=green!40!black] (3.5,4.5) circle (0.3cm);"
\end{tikzpicture}

\end{document}