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