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