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