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