One vertex per element, one color per generator, with an edge from x to x·s.
(2,6)(3,4)(7,8)(9,10)(11,21)(12,26)(13,20)(14,19)(15,18)(16,24)(17,28)(22,36)(23,32)(25,31)(27,33)(29,34)(30,37)(35,39)(38,40) involution — undirected(1,2,5,8)(3,6,4,7)(9,11,15,23)(10,16,18,31)(12,22,29,37)(13,25,14,24)(17,30,33,36)(19,32,20,21)(26,40,34,35)(27,39,28,38)(9,12,15,29)(10,17,18,33)(11,22,23,37)(13,28,14,27)(16,30,31,36)(19,26,20,34)(21,35,32,40)(24,39,25,38)(10,18)(16,31)(17,33)(19,20)(21,32)(26,34)(30,36)(35,40) involution — undirected(1,3,5,4)(2,7,8,6)(10,18)(11,23)(17,33)(19,20)(22,37)(24,25)(26,34)(38,39)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.