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