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