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