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