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