For question 1, use the shade option to set another color, and for question 2, use the overlap to set a negative value. For the color, you'd better use a light one for which you could give an ordinary color with a suitable percent.
\documentclass{article}
\usepackage{venndiagram}
\begin{document}
\begin{venndiagram2sets}[showframe=false,shade=blue!20,overlap=-0.5cm]
\fillA\fillB
\end{venndiagram2sets}
\begin{venndiagram2sets}[shade=blue!20,overlap=-0.5cm]
\fillA\fillB
\end{venndiagram2sets}
\end{document}

If you want to fill the sets with different colors, I advise you to use the tikz package to draw Venn diagrams since it could supply more choices. For example,
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\draw[circle, thick,fill=red,fill opacity=0.2] (0,0) circle (1.5cm) node {};
\node at (0,1) (A) {$A$};
\draw[circle, thick,fill=blue,fill opacity=0.2] (4,0) circle (1.5cm) node {};
\node at (4,1) (B) {$B$};
\end{tikzpicture}
\par\vspace{3cm}
\begin{tikzpicture}
\draw[circle, thick,fill=red,fill opacity=0.2] (0,0) circle (1.5cm) node {};
\node at (0,1) (A) {$A$};
\draw[circle, thick,fill=blue,fill opacity=0.2] (2,0) circle (1.5cm) node {};
\node at (2,1) (B) {$B$};
\end{tikzpicture}
\end{document}

By the way, when to ask a question next time please give a minimal working sample which could be compiled, and then others could answer it more conveniently.