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