Hi in Desktop Photoshop it is very easy to isolate the black (or Colour) from a a black & white line art image by command clicking the channel. I see no equivalent of this in Fresco. It seems that a channel pallet is a necessity?
Fresco is a drawing app more than a file manipulation app. To me anyway. I don't think it needs all the same features as Photoshop, specially now with Photoshop being available on the iPad as well. To make this request though you'd be best to post a suggestion on the Fresco UserVoice page.