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