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