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