Update src/7_tight_binding_model_sol.md

src/7_tight_binding_model_sol.md

@@ -46,7 +46,7 @@ pyplot.tight_layout();
 pyplot.subplot(1,2,2)
 w = np.linspace(-0.95, 0.95, 300);
 g = 1/np.sqrt(1-w**2);
-pyplot.plot(w, g);
+pyplot.plot(w, g, 'b');
 pyplot.xlabel(r'$\omega$'); pyplot.ylabel('$g(w)$');
 pyplot.xticks([-1, 0, 1], [r'$-2\sqrt{\frac{k}{m}}$', 0, r'$2\sqrt{\frac{k}{m}}$']);
 pyplot.yticks([0.5, 1], [0, r'$\frac{L}{2\pi a}\sqrt{\frac{\kappa}{m}}$']);