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