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