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