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)(19,31)(23,32)(25,33)(27,40)(29,37)(30,36)(34,39)(35,38) involution — undirected(9,11,14,24,15,12,16,25)(10,17,20,18,21,33,22,26)(13,23,29,38,30,27,31,39)(19,32,36,34,37,40,28,35)(1,2,3,4)(9,12)(10,18)(11,15)(13,23)(14,25)(16,24)(17,22)(19,35)(20,33)(21,26)(27,30)(28,40)(29,38)(31,39)(32,36)(34,37)(6,8)(9,13,14,29,15,30,16,31)(10,19,20,36,21,37,22,28)(11,23,24,38,12,27,25,39)(17,32,18,34,33,40,26,35)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.