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