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