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