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