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