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