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