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