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