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