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