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