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