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