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