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