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