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