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