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