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)(27,30)(28,31)(29,32)(33,36)(34,37)(35,39)(38,40)(1,3)(2,6)(4,7)(5,8)(9,10,13,15)(11,12,16,14)(17,18,20,22)(19,21,23,24)(26,27)(29,37)(31,33)(35,38)(2,7)(3,8)(9,11,13,16)(10,14,15,12)(17,18)(19,21)(20,22)(23,24)(25,27,30,26)(28,33,36,31)(29,34,37,32)(35,40,38,39)(1,3)(2,4)(5,8)(6,7)(9,11)(10,12)(13,16)(14,15)(25,28,30,36)(26,31,27,33)(29,38,37,35)(32,40,34,39)(1,4)(2,3)(5,6)(7,8)(9,12)(10,11)(13,14)(15,16)(17,19,20,23)(18,21,22,24)(25,29,30,37)(26,32,27,34)(28,35,36,38)(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.