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