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