I think certain people who achieve a certain connection with Allah have noor on their face. As to who can see it, the person seeing it probably must be a certain level too! One brother once told us that one day, while sitting in Nizamuddin, there suddenly came a huge amount of noor and tranquility in the markaz. Looking up, he saw that Hadhrat Ji Maulana Inaam ul Hasan and Maulana Umar Palanpuri were returning from their walk. I've also heard - I don't know how accurate this is - that there are different colors of noor, and people with a very high status can see the different colors of noor on people. Anyone heard about that before?