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