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