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