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)(12,26)(13,14)(17,30)(19,20)(24,25)(27,28)(29,33)(31,36)(35,37)(39,40) involution — undirected(9,10,14,19,15,20,13,16)(11,22,24,17,25,32,21,30)(12,18,26,33,28,34,27,29)(23,36,37,31,38,40,35,39)(2,5)(6,8)(9,11,14,24,15,25,13,21)(10,17,16,22,20,30,19,32)(12,23,26,37,28,38,27,35)(18,31,29,36,34,39,33,40)(1,3,4,7)(2,6,5,8)(9,12,13,27,15,28,14,26)(10,18,16,29,20,34,19,33)(11,23,21,35,25,38,24,37)(17,31,22,36,30,39,32,40)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.