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