\documentclass{standalone}

\usepackage{tikz}
\usepackage{shapes}

\begin{document}
\begin{tikzpicture}
  \grid{7}{7}{(-2,-2)}

  \Staircase{cyan}{(0,0)}

  \square{green}{(0,-1)}
  \square{green}{(1,-1)}
  \square{green}{(2,-1)}
  \square{green}{(3,-1)}

  \square{magenta}{(-1,0)}
  \square{magenta}{(-1,1)}
  \square{magenta}{(-1,2)}
  \square{magenta}{(-1,3)}

  \square{yellow}{(3,1)}
  \square{yellow}{(2,2)}
  \square{yellow}{(1,3)}

  \square{lightgray}{(0,4)}
  \square{lightgray}{(4,0)}

\end{tikzpicture}
\end{document}