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