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