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