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