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