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