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