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