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