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