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