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)(11,18)(12,22)(13,16)(14,17)(15,20)(19,23)(21,24)(25,26,31,38,29,28,30,33)(27,34,39,35,36,32,37,40)(2,5)(6,8)(9,11,14,21,13,20,12,19)(10,15,17,23,16,18,22,24)(25,27,30,37,29,36,31,39)(26,32,33,35,28,34,38,40)(1,3)(2,6)(4,7)(5,8)(10,16)(11,19)(12,14)(15,23)(18,24)(20,21)(25,28,29,26)(27,35,36,40)(30,33,31,38)(32,39,34,37)(3,7)(6,8)(9,12,13,14)(10,17,16,22)(11,19,20,21)(15,23,18,24)(26,28)(27,36)(33,38)(37,39)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.