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