I have found a resource for caramel coloring that is a lot less than $1.50 per bottle.  It was at my local oriental grocery store (who'd a thunk it?) in their flavorings section.  Made by Wang, in Korea, it gives a real depth of color to the darker half of my marbled rye bread that I couldn't get with cocoa.  It is a fairly viscous syrup and I'm pleased with the find.