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