A color copy background, sometimes called a laser 
copy background, is pretty much what it sounds 
like: a color photocopy of the (hopefully) 
original matching background.  They aree lower 
value than a cel with the original background, 
but prefered to no background at all.  Paper is 
thinner, but I wouldn't say any better or worse 
than an original background, except maybe that 
there is no paint to seep into the cel.  I still 
keep them seperate though.