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