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