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