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