\documentclass[12pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz,pgffor}
\begin{document}
\begin{tikzpicture}
\pgfmathdeclarerandomlist{MyColors}{%
{red}%
{magenta}%
{olive}%
{brown}%
{violet}%
{gray}%
{purple}%
{yellow}%
{orange}%
{cyan}%
{green}%
{blue}% 
}
\clip (5,5) circle (5cm);
\foreach \i in {0,1,...,10}{
	\foreach \j in {0,1,...,10}{
		\pgfmathparse{10*rnd}\let\x\pgfmathresult
		\pgfmathparse{10*rnd}\let\y\pgfmathresult
		\pgfmathrandomitem{\RandomColor}{MyColors}
		\fill[\RandomColor] (\x,\y) circle (5mm);
	}
}
\end{tikzpicture}

\begin{tikzpicture}
\clip (5,5) circle (5cm);
\foreach \i in {0,1,...,10}{
	\foreach \j in {0,1,...,10}{
		\pgfmathparse{10*rnd}\let\x\pgfmathresult
		\pgfmathparse{10*rnd}\let\y\pgfmathresult
		\pgfmathrandomitem{\RandomColor}{MyColors}
		\fill[ball color=\RandomColor] (\x,\y) circle (5mm);
	}
}
\end{tikzpicture}
\end{document}