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