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