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