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