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