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