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)(11,15)(12,19)(13,14)(16,20)(17,21)(18,24)(22,23)(25,26)(27,32)(28,29)(30,38)(31,33)(34,40)(35,37)(36,39) involution — undirected(2,5)(6,7)(11,17)(15,21)(18,23)(22,24)(25,27,31,28)(26,32,33,29)(30,35,40,36)(34,39,38,37)(1,2)(3,6)(4,5)(7,8)(10,14)(15,21)(16,19)(22,24)(26,33)(27,28)(34,38)(35,36) involution — undirected(1,3,4,8)(2,6,5,7)(9,10)(11,15)(12,16)(13,14)(17,21)(18,22)(19,20)(23,24)(25,28,31,27)(26,29,33,32)(30,36,40,35)(34,37,38,39)(9,11,13,17)(10,15,14,21)(12,18,20,23)(16,22,19,24)(25,29)(26,28)(27,33)(30,39)(31,32)(34,35)(36,38)(37,40)(9,12)(10,16)(11,18)(13,20)(14,19)(15,22)(17,23)(21,24)(25,30,31,40)(26,34,33,38)(27,35,28,36)(29,37,32,39)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.