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