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