[Hampshire] Colour depth

How can I tell what the colour depth (16, 24, 32 bit etc.) I am using. I know
I can look at xorg.conf but how do I know it is using what I tell it to use??

For the record I am using an ATI 1600 Pro but using Vesa drivers on mepis 7
(debian etch) and my monitor is Viewsonic 19" VA903b

Tim