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