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