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