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