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