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