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