One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(5,6)(7,8)(9,10)(11,23)(12,29)(13,31)(14,22)(15,21)(16,20)(17,26)(18,19)(24,25)(27,36)(28,35)(30,33)(32,34)(37,39)(38,40) involution — undirected(2,4)(9,11,14,28,15,27,16,26)(10,17,22,23,21,35,20,36)(12,30,32,24,19,38,31,39)(13,33,29,25,34,40,18,37)(1,2,3,4)(9,12)(10,18)(11,24)(13,20)(14,31)(15,19)(16,32)(17,33)(21,29)(22,34)(23,37)(25,36)(26,38)(27,39)(28,30)(35,40)(6,8)(9,13,16,18,15,34,14,29)(10,19,22,31,21,12,20,32)(11,25,28,40,27,37,26,33)(17,24,36,30,35,39,23,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.