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