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