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