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