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