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