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