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