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