Quiver plots and line plots do not use the colormap used by colorbar. You have to explicitly set both the axes 'colororder' and 'colormap' properties to the same map.
load('wind','x','y','u','v')
X = x(11:22,11:22,1);
Y = y(11:22,11:22,1);
hold on
quiver(X,Y,u(11:22,11:22,1),v(11:22,11:22,1));
quiver(X,Y,u(11:22,11:22,2),v(11:22,11:22,2));
quiver(X,Y,u(11:22,11:22,3),v(11:22,11:22,3));
quiver(X,Y,u(11:22,11:22,4),v(11:22,11:22,4));
colormap(get(gca,'colororder'))
colorbar
That said, that's really what the legend is for. In this case, the colorbar scale has no clear meaning.
Still, I'm not sure if that's what you're asking for. "I am trying to use the colour bar to represent the U and V values" might mean that you're trying to describe the vector fields using some solid color map (like pcolor() or something). If that's the case, you'll have to actually do that.
figure
hold on
pcolor(X,Y,hypot(u(11:22,11:22,1),v(11:22,11:22,1)));
quiver(X,Y,u(11:22,11:22,1),v(11:22,11:22,1));
shading interp
colormap(gray(256))
colorbar
Note that I only plotted one quiver plot and the pcolor() plot shows only the vector magnitude. Trying to put more things into the same plot should raise the question of how they're expected to be represented clearly.
If you want to represent the vector field (both components) with pcolor(), then you might want to look at this discussion:
