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