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