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