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