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