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