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