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