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