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