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