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