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