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