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