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