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