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