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