\begin{table}%t3
\caption{\label{table:3}Intrinsic and visible colour indices of \mbox{M~31}.}
%\centering
\small 
\begin{tabular}{lllll}
  \hline\hline \noalign{\smallskip}
  \mbox{M~31} & $U-B$ & $B-V$ & $V-R$ & $R-I$ \\
  & (mag) & (mag) & (mag) & (mag) \\ 
  \hline 
  Intrinsic & 0.30 & 0.60 & 0.76 & 0.28\\ 
  Visible &  0.33 & 0.63 & 0.81 & 0.31\\
  \hline
\end{tabular}
\end{table}