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