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