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)(13,17)(16,19)(18,23)(20,22)(21,24) involution — undirected(1,2)(3,6)(4,5)(7,8)(9,11,14,19)(10,15,12,16)(13,21,22,18)(17,24,20,23)(26,31)(29,37)(32,33)(35,36)(1,3,4,7)(2,6,5,8)(9,11)(10,16)(12,15)(13,18)(14,19)(17,24)(20,23)(21,22)(25,26)(27,33)(28,32)(29,34)(30,31)(35,40)(36,39)(37,38)(25,27,30,28)(26,32,31,33)(29,35,37,36)(34,39,38,40)(9,12,14,10)(11,16,19,15)(13,20,22,17)(18,24,21,23)(25,28,30,27)(26,33,31,32)(29,36,37,35)(34,40,38,39)(9,13,14,22)(10,17,12,20)(11,18,19,21)(15,23,16,24)(25,29,30,37)(26,34,31,38)(27,35,28,36)(32,39,33,40)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.