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