Tim,
RCAF Catalina color scheme in Ceylon apparently was a dark tone. See e.g.
http://www.junobeach.org/e/4/can-tac-air-coa-e.htm#null
(You can open the the picture of the Cat to get a full view).
There are also pictures of Leonard Birchall sitting in his cockpit of the Catalina he spotted the Japanese fleet in, and this a/c also has a dark scheme.
See e.g. here:
http://www.airforce.forces.gc.ca/sit..._e.asp?id=1511
Regards,
Leendert