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