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