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