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