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