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)(27,33)(28,34)(29,31)(30,32)(35,38)(36,39)(37,40) involution — undirected(2,5)(3,7)(9,11,13,19)(10,14,16,17)(12,20,21,18)(15,23,24,22)(26,31)(27,35)(32,34)(36,37)(1,2)(3,6)(4,5)(7,8)(26,32)(27,35)(28,30)(31,34)(33,40)(38,39) involution — undirected(2,5)(6,8)(9,12,13,21)(10,15,16,24)(11,18,19,20)(14,22,17,23)(25,27)(26,33)(28,37)(29,35)(30,36)(31,38)(32,39)(34,40)(1,3,4,7)(2,6,5,8)(10,16)(14,17)(15,24)(22,23)(25,28,29,30)(26,32,31,34)(27,36,35,37)(33,40,38,39)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.