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