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