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