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