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