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