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