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