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)(11,20,22,15,23,29,37,30)(12,16,26,24,25,31,38,32)(21,33,36,28,35,34,40,39)(2,5)(3,7)(9,10)(11,15)(12,24)(13,18)(14,19)(16,26)(17,27)(20,22)(21,34)(23,30)(25,32)(28,36)(29,37)(31,38)(33,35)(39,40) involution — undirected(1,2)(3,6)(4,5)(7,8)(9,11,13,22,14,23,27,37)(10,15,18,20,19,30,17,29)(12,21,26,36,25,35,38,40)(16,28,32,33,31,39,24,34)(2,5)(6,8)(9,12,13,26,14,25,27,38)(10,16,17,24,19,31,18,32)(11,21,22,36,23,35,37,40)(15,28,29,34,30,39,20,33)(1,3,4,7)(2,6,5,8)(12,25)(16,31)(21,35)(24,32)(26,38)(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.