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