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