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