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