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