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