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