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