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