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