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