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