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