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