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