This is a modified version of the function quiver [from C.M. Thompson] to plot velocity vectors as arrows with components (u,v) at the points (x,y) with the color corresponding to the magnitude of the vector and using the current colormap.

Tip: for best results, add set(gcf, 'InvertHardCopy', 'off') after the function to keep the black background on the hardcopy. See attached examples.