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