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