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)(11,17)(12,20)(13,14)(15,19)(16,21)(18,22)(23,24)(26,30)(27,33)(28,36)(37,40) involution — undirected(1,2,4,6)(3,5,8,7)(9,11,14,19)(10,15,13,17)(12,18,21,24)(16,22,20,23)(25,26,31,30)(27,34,33,29)(28,32,36,38)(35,40,39,37)(1,2)(3,5)(4,6)(7,8)(12,21)(16,20)(18,24)(22,23)(25,27)(26,29)(28,35)(30,34)(31,33)(32,37)(36,39)(38,40) involution — undirected(1,3)(2,5)(4,8)(6,7)(9,12,14,21)(10,16,13,20)(11,18,19,24)(15,22,17,23)(25,28)(26,32)(27,35)(29,37)(30,38)(31,36)(33,39)(34,40)(9,13,14,10)(11,15,19,17)(12,20,21,16)(18,22,24,23)(25,29,31,34)(26,33,30,27)(28,37,36,40)(32,39,38,35)(9,11)(10,17)(12,18)(13,15)(14,19)(16,23)(20,22)(21,24)(25,30,31,26)(27,34,33,29)(28,38,36,32)(35,40,39,37)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.