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