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