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