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