Thanks, Martin!
Actually it is a feature. Patterns are uncoloured now (see PDF reference for Uncolored tiling patterns) to allow the application of symbol-color command on patterns.
Now you need to define just the shape of all symbols in Metapost and color of any symbol in layout, which is much more flexible. It wouldn't work for patterns consisting of more than one colour, but nobody has complained so far.
OK, makes sense (although according to the manual symbol-color is a new command in 5.3, while as far as I can tell, pattern fills have been black-only since 5.2.11). Anyway, the manual specifies: symbol-colo[u]r <point/line/area/group/special> <symbol-type> <colour> so in my test piece I tried: symbol-color area u:test [1.0 0 0] and I get the following error message: unknown symbol specification -- area u:test What am I doing wrong? Duncan