% adapted from:
% http://www.csupomona.edu/~jrfisher/www/prolog_tutorial/pt_framer.html
%    section 3.2

part(a). 
part(b). 
part(c).

red(a). 
black(b).

color(P,red) :- red(P),!.
color(P,black) :- black(P),!.
color(P,unknown).