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