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