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