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