The eye is a very delicate part of the body and it should be safeguarded to the best possible extent.
If you notice a colored circle around the pupil of the eye, then it is definitely not a normal thing.
It actually signifies the rarest eye disorder to be found.
Since it is a rare disorder, there is no cure too.
It is not exactly a disease.
Instead you can call is a medical condition.
Several times this type of ring is not easily recognized when people look into bright light.
In case you have been seeing an abnormal circle around the pupil, then you should immediately contact an eye specialist or a doctor.
Even the DNA in your body can be tested to find abnormalities.
The reason could be anything from a serious disorder to a grave one.
It could be Wilson's disease which is a rare genetic disorder and is caused because the body is prevented from excreting copper and the mineral is retained by the body.
The possible reasons could also be heterochromia.
It is a genetic condition where the color of the pupil is naturally different than the normal pupil.
This kind of coloration is also seen in the hair.
It is most apparent in the eyes.
Wilson's disease though being a genetic disorder has some kind of treatment available.
However if it is naturally occurring condition then one cannot do much.
However it is always better to get the cause checked.
Sometime it can be an underlying eye problem too.