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