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