You can colour edges in exactly the same way that you can colour faces...although you'll need to do it in wireframe, as the paint bucket much prefers to affect faces first.
In order to see the coloured edges you'll need to change the setting in the Styles palette/Edges tab from 'All the same' to 'By material' as in the attached file.
PS. This ability to paint edges is the reason that it is sometimes necessary to individually delete materials from the Materials palette, even after having purged your model. If you have materials still left there, registering an area of 0...but refusing to purge, it's most likely because they are painted onto edges...but you can't see that, because the usual practice is to have all edges showing as black, irrespective of their real colour.
redoutline.jpg