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