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)(25,26,30,32,28,33,29,34)(27,35,38,39,36,31,37,40)(2,5)(6,7)(9,11,12,23,13,22,14,21)(10,15,19,16,18,20,17,24)(25,27,29,37,28,36,30,38)(26,31,34,39,33,35,32,40)(9,11,13,22)(10,16,18,24)(12,21,14,23)(15,17,20,19)(26,32)(27,36)(29,30)(31,39)(33,34)(35,40)(1,3,4,8)(2,6,5,7)(9,12,13,14)(10,17,18,19)(11,21,22,23)(15,16,20,24)(26,33)(27,36)(32,34)(37,38)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.