gistfile1.txt

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{backgrounds}
\begin{document}

What you have now:

\tikz\fill[blue](0,0)circle(1); \kern-0.5cm\tikz \fill[red](0,0)circle(1);

What you want to do:

\begin{tikzpicture}
\fill[blue](0,0)circle(1);
\scoped[on background layer]
  \fill[red](1.5,0)circle(1);
\end{tikzpicture}

My inconvenient, hacky suggestion:

\hspace{1.75cm}\tikz\fill[red](0,0)circle(1); \hspace{-3.75cm}\tikz \fill[blue](0,0)circle(1);
\end{document}