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