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