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