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