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