How Can I Fix Hypopigmentation After VBeam?

The loss of "color" to the skin, in your case, is most likely from reducing the number of microcapilaries with the laser. Loss of pigmentation following laser treatment can also be caused by depletion of the melanin production cells in your skin. Hypopigmentation may take months to improve, but it can be permenent. Presently, I would suggest specific skin concealers for blending. Sun Protection is also recommended.

What you are experiencing is actually the result of the VBeam working in that spot. It knocked out all the redness and the blood vessels in that area. Unfortunately, now it looks very white compared to the rest of your skin which has a more ruddy/pink undertone.  The only thing to do is to try IPL to the remainder of your forehead or using the VBeam to eliminate the ruddy tone on your forehead or at least feather out the white area to pink.

Let me first say, a personal evaluation is important to get a truly accurate picture of your problem. What you are describing sounds like an "excellent" laser response, but a poor cosmetic result. The laser was effective at reducing the vessels in that one area, just too much so compared to your surrounding skin.
A series of full face V-Beam treatments at non-purpuric settings would be useful in decreasing the redness you continue to note on the rest of your face, thereby blending to one consistent color.