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)(25,26,29,33,30,34,40,32)(27,28,35,39,37,31,36,38)(2,5)(6,8)(9,11)(10,14)(12,19)(13,18)(15,21)(16,17)(20,24)(22,23)(25,27)(26,31)(28,34)(29,35)(30,37)(32,39)(33,38)(36,40) involution — undirected(11,18)(14,17)(19,24)(21,23)(25,28,30,31)(26,27,34,37)(29,38,40,39)(32,35,33,36)(1,3,4,7)(2,6,5,8)(12,20)(15,22)(19,24)(21,23)(25,29,30,40)(26,32,34,33)(27,35,37,36)(28,38,31,39)(9,12,13,20)(10,15,16,22)(11,19,18,24)(14,21,17,23)(25,29,30,40)(26,33,34,32)(27,36,37,35)(28,38,31,39)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.