depends what software you have
Photoshop try Image,Mode,Colour Table.
You probably have to save the image and load the file, rather than just copying.
It's what _Felix uncovered below
(
Bloop Fri 16 Jul, 22:10,
Tue 3 Feb 2009, 1:02,
archived)
aha
i can sleep contented now
nn
(
Rebel biscuit stercore sumus et nos esse novimus,
Tue 3 Feb 2009, 1:05,
archived)