Hi, welcome to the forum, the common causes of such discoloration would be Infectious keratitis, Bacterial keratitis, Viral keratitis, Iritis and Subconjunctival hemorrhage. It can start with the red eye and later due to blood
pigment changes it can stain
brown. It can be seen in allergic conditions. It can occur spontaneously or with Valsalva associated with coughing, sneezing, straining, or vomiting.
Vexol helps to reduce the inflammation.