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