There exists "color altloc": no altloc = red, %A=green, %B=blue.
But easy enough to make my own color scheme.

1ldn: Why does Jmol menu have 8 configs, yet config=1 has all atoms? 
There are %A - %H, 20 atoms each.

%A/B or CONF N can be a load filter.

Issues:

manual says "config [1]" but what works is config=1
manual says %? but this is invalid.
% and not % work.
% requires upper case (but probably shouldn't).
altloc = A same as %A

config=0 selects all but is supposed to select "all atoms having
configs" (it says under atom properties)?

manual should be clear that config=1 selects atoms with one config
plus the first config of atoms with more than one.
Thus config=1 and !% selects the first config of only those atoms with
more than one config.

When %A and %B and no atoms without altloc, config 1 includes %A. (3hyd)
  In 3hyd, "config=1 and not %" gives 11, same ad %A.
When %A and same atoms without altloc, config 1 ????
% is atoms without altloc, and "not %" is atoms with altloc.
%1 does not select %A.

Is there some way to select atoms without altloc that also have altloc?
e.g. .SG, .SG%A vs. .SG%A, .SG%B

if {not % and not config=1) #altloc not in config=1
equals an integral multiple of (not % and config=1)
then probably there are no atoms lacking altloc codes corresponding to
atoms with altloc codes.
equals (not % and config=2) #altloc and config


When there are no altlocs, config=1 selects all atoms, and config=2 selects
none.

%a should not be case dependent since there are never more than a few altlocs.
---------------

config=1 atoms with only one config + first config for those having more than 1.

% selects atoms with only one config
%A selects atoms wtih config A (case sensitive! so %a doesn't work with 3hyd).