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