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