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