In the library module, in the filters just above the filmstrip, I noticed the usual colours (red/yellow etc) but also black and white. But when I go to assign colours to images from the toolbar, black or white is not an option?
Those are to let you filter on a) no label (the blackish gray one) and b) a custom label.
More info on custom labels are here:
http://www.image-space.com/Lightroom_Tips_Tricks/Library_Module_Tips/color_label_sets/color_label_sets.html
