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