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