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