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