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