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