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