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