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)(27,31)(28,32)(29,30)(33,38)(34,37)(35,36)(39,40)(1,3,6,4)(2,5,7,8)(9,10)(11,12)(13,14)(15,16)(18,21)(22,24)(26,30)(28,35)(31,37)(33,39)(2,7)(3,4)(10,14)(11,15)(17,18)(19,22)(20,21)(23,24)(25,26)(27,31)(28,36)(29,30)(32,35)(33,40)(34,37)(38,39) involution — undirected(1,4,6,3)(2,5,7,8)(9,11,13,15)(10,12,14,16)(25,27,29,34)(26,31,30,37)(28,33,35,39)(32,38,36,40)(1,5)(2,3)(4,7)(6,8)(9,12)(10,15)(11,14)(13,16)(17,19)(18,22)(20,23)(21,24)(25,28,29,35)(26,32,30,36)(27,33,34,39)(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.