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