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