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