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