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