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