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