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