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