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