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