I need to do a Darth Vadar FBCT for a friend's cake. I always use just regular store bought fudge icing for the outline of each FBCT, so could I just use that for the black on Darth Vadar? I'm not making choc BC, so I thought it would be really tough to get my regular BC colored black.

Any thoughts out there?

Thanks!

Certainly go ahead Should be no problem.
You can add some blk paste/gel to the choco canned icing for a nice, dark color.

Hint: save all your tiny dibs and dabs of icing in the fzr until you want some dk brown or black. Stir it well; it will be an ugly 'cameo' color; add paste/gel.
Do this the night before (or early in the day) so the color has time to 'develope'. It will turn darker the longer it has to sit & when air hits it. It's best to keep some black on hand in the fzr just for things like this.
Another option is to buy a tube of Wilton black. It is soooooo color satuated you can mix it w/an equal amount of any color icing and still have a nice, dark tone. Granted, this will work only for small amounts - not for a whole cake