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