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