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