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