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