Source PostScript (ifputcolors.pps)

%% syntaxe : solid str1 str2 bool ifputoutcolors --> -
%% colorie en str1 si <> de str2
/ifputincolors {
   1 ifputc@l@rs
} def

/ifputoutcolors {
   2 ifputc@l@rs
} def

 /ifputc@l@rs {
10 dict begin
   2 eq {
      /getcol {solidgetoutcolors} def
      /putcol {solidputoutcolors} def
   } {
      /getcol {solidgetincolors} def
      /putcol {solidputincolors} def
   } ifelse
   /bool exch def
   /str2 exch def
   /str1 exch def
   /solid exch def
   /FC solid getcol def
   0 1 FC length 1 sub {
      /i exch def
      FC i get str2 search {
         /correspondance true def
         pop pop pop
      } {
         /correspondance false def
 	pop
      } ifelse
      correspondance bool and
      correspondance not bool not and
      or {
         FC i str1 put
      } if
   } for
   solid FC putcol
end
} def