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