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