\documentclass{standalone}
\usepackage{tikz}
\usepackage{grid}

\begin{document}
\begin{tikzpicture}
  \fillsquare{(0,0.5)}5{red}
  \fillsquare{(0,-0.5)}5{red}
  \fillsquare{(3,2.5)}5{red}
  \fillsquare{(3,3.5)}5{red}
  \fillsquare{(6,2.5)}5{red}
  \fillsquare{(6,3.5)}5{red}

  \fillsquare{(0,0)}4{cyan}
  \fillsquare{(3,3)}4{cyan}
  \fillsquare{(6,3)}4{cyan}

  \grid{(-3,-3.5)}{0.5}{24}{20}
\end{tikzpicture}
\end{document}