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