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