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