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)(15,17)(16,22)(23,24)(26,31)(27,34)(29,37)(36,39) involution — undirected(1,2,4,6)(3,5,8,7)(9,10)(11,15)(12,16)(13,14)(17,19)(18,23)(20,24)(21,22)(25,26,30,31)(27,28,34,32)(29,33,37,38)(35,36,40,39)(1,2)(3,5)(4,6)(7,8)(25,27,30,34)(26,32,31,28)(29,35,37,40)(33,39,38,36)(1,3,4,8)(2,5,6,7)(9,10)(11,17)(12,16)(13,14)(15,19)(18,24)(20,23)(21,22)(25,27)(26,28)(29,35)(30,34)(31,32)(33,36)(37,40)(38,39)(9,11,13,19)(10,15,14,17)(12,20,21,18)(16,24,22,23)(25,28)(26,27)(29,36)(30,32)(31,34)(33,35)(37,39)(38,40)(9,12,13,21)(10,16,14,22)(11,18,19,20)(15,23,17,24)(25,29)(26,33)(27,35)(28,36)(30,37)(31,38)(32,39)(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.