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