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