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