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