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