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