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