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