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