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