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