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