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