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