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