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