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