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