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