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