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