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