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