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