IPL can be done with extremely caution in patients with vitilito. The one thing to consider is that vitiligo can spread in traumatized areas. If there is inflammation or a burn from IPL, a spot of vitiligo may start in that area.
It also depends on what you are trying to accomplish by an IPL treatment. If you want to treat redness, with caution and proper settings, it can be done. If you are trying to remove brown to even out skin tone, there are other methods of doing that.
Please consult with a board-certified dermatologist or plastic surgeon with training and experience in IPL treatments.
The most important thing you can do for areas of vitiligo is protect them from UV damage from the sun. Since they have no pigment, they are much more susceptible to skin cancer than pigmented areas.