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