\begin{table}
\caption{Range of the applicable $B-V$ colours for the selected classes of objects}\label{colours}
\begin{tabular}{|c|c|c|c|} \hline
CLASS	& $(B-V)$		& $(B-V)$		& REFERENCE			\\
	& min		& max		&				\\ \hline
Stars	& $-$0.2		& +1.8		& \citet{Hipparcos97}		\\
WDs	& $-$0.3		& +1.6		& \citet{Bergeron+95}		\\
CVs	& +0.2		& +2.0		& \citet{HendenHoneycutt95}	\\
Galaxies& +0.2		& +1.6		& \citet{PrugnielHeraudeau98}	\\
Clusters& +1.0		& +1.5		& \citet{Chieregato05}		\\
AGN	& $-$0.6		& +1.6		& \citet{Veron-CettyVeron03}	\\ \hline
\end{tabular}
\end{table}