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