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