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