I just read an article on the Sky&Telescope website about the photographic discovery of a dwarf galaxy near NGC 253 by an Australian amateur astronomer:
According to this paper the magnitudes are: red 15.0 +/- 0.5 mag, green 15.9 +/- 0.5 mag; radius 3.24 +/- 0.51 arcmin, visual surface brightness 26.5 +/- 0.7 mag/sqarcsec.