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