It's supposed to. Black is toilet and shower, gray is kitchen and bathroom sinks, and the extra gray button on the panel is for a tank you don't have. The XLR factory uses the same indicator panel for all their units, and some upper end models have 2 gray tanks. Yours does not.
Shower draining to black is a good thing. More water is your friend for draining and rinsing.
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)