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