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