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)(27,35)(28,34)(29,33)(30,32)(31,36)(37,40)(38,39) 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)(26,31)(28,37)(29,36)(30,38)(32,40)(33,35)(34,39)(3,8)(5,7)(9,11,13,18)(10,15,14,21)(12,20,19,17)(16,24,22,23)(26,32)(27,36)(28,30)(31,39)(33,34)(35,40)(2,6)(5,7)(9,12,13,19)(10,16,14,22)(11,17,18,20)(15,23,21,24)(26,33)(27,36)(32,34)(37,38)(10,14)(15,21)(16,22)(23,24)(25,28,29,30)(26,34,33,32)(27,37,36,38)(31,39,35,40)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.