Blue sclera is a "sign" not a symptom. Causes of blue sclera are too numerous to list. See an Ophthalmologist to determine if you have a problem, this is an MD physician that takes care of the eye.
An extended list of the causes of blue sclera can be found in :
OcularMelanoma of the eye
Ocular lubricant
Tonometry Differential Diagnosis by Frederick Hampton Roy MD (Williams & Wilkins publisher). 6th Edition page 265-268
John C. Hagan III MD eye physician and surgeon