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