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