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