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