Visual inspection of Retension Sample

At our site, one of the product required to fill in Amber colored glass vial.
Retension samples from the each product batch are being taken and store at predefined storage condition.
Suggest what is the procedure to perform Description or product color appearance test from Amber color vial?

It is required to visually observe appearance of the poduct every year from the retention samples of vials. Since the vials are ambar coloured it would be difficult to observe the contents filled in the vials. Therefore, I can suggest that the (say 1 or 2 vias) vials should be opened and the contents should be taken out on white paper and seen against strong white light. And note for any discolouration, lump / cake formation in case of powder and any discolouratrion or generation of particles, crystallization of the product, any microbial growth etc.
Considering this aspect sufficient number of vials from every batch should be kept as retention samples. Opened vials after visual observation should not be reused and must be dicarded.