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