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