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