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