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