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