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