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