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