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