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