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)(27,34)(28,32)(29,31)(30,35)(33,37)(36,38)(39,40) 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)(26,30)(28,35)(29,36)(31,39)(32,34)(33,38)(37,40)(1,3)(2,5)(4,8)(6,7)(9,12,14,18)(10,16,17,13)(11,20,22,24)(15,21,19,23)(26,31)(27,35)(29,37)(30,38)(32,33)(34,39)(3,8)(5,7)(10,17)(12,18)(15,19)(20,24)(26,32)(30,34)(31,33)(38,39) involution — undirected(2,6)(5,7)(9,13,14,16)(10,18,17,12)(11,21,22,23)(15,20,19,24)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.