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