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