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