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)(17,28)(22,31)(24,32)(25,30)(27,34)(29,33)(35,38)(36,39)(37,40) involution — undirected(2,5)(6,8)(9,11,14,25,15,24,13,23)(10,16,20,32,19,30,18,21)(12,22,28,38,29,37,27,36)(17,31,26,39,34,40,33,35)(16,30)(21,32)(31,40)(35,39) involution — undirected(1,3,4,7)(2,6,5,8)(9,12,13,27,15,29,14,28)(10,17,18,33,19,34,20,26)(11,22,23,36,24,37,25,38)(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.