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