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