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