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