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