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