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