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