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