% Venn diagramm with PGF 3.0 blend mode
% Author: Paul Gaborit
\documentclass[tikz,border=10pt]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[blend group=screen]
  \fill[red!90!black]   ( 90:.6) circle (1);
  \fill[green!80!black] (210:.6) circle (1);
  \fill[blue!90!black] (330:.6) circle (1);
\end{tikzpicture}
\end{document}
