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