Description of Ciprofloxacin injection is light yellow. If concentration of the product is higher, i.e. 1%, this color is more apparent.
The problem here is container to container variation of color. Root cause of which can not be assigned to material, machine or man as per your investigation.
You may try to reduce dissolve oxygen / head space oxygen content. I think there is oxygen content variation amoungst vials in same batch. The Oxygen may be reacting with one of the ingredient of the formulation and changing colour.