Hello, I have the 1/35 tamiya panther g late that was given to me by a friend and periscopes come with the kit but are not in clear plastic. I would like to know should i make new periscopes or is there some kind of way i can paint them to give illusion of that effect. Thanks for help, Steve

Couple of options.
Paint them as is, with a dark yellow or dark grey body and a prismatic silver 'glass'

I have used Vallejo Silver paint and added layers of green and blue Tamiya clear paint or Vis a Vis overhead marker.

Other options include the Fine Molds Clear plastic scopes, mask off the glass, paint the body silver, and overcoat with the outer color, then remove the masks.

Aber makes very nice PE scopes and brackets, but these need some type of 'glass' installed. Krystal Kleer , etc..

World War Two tank periscopes do not look silver. They are designed to transmit light into the vehicle, not reflect it out again (the mirror is angled down). In real life, periscope glass looks gloss black, unless it is on a modern vehicle, which would have a pink or orange coating to reflect laser beams (to protect the crew's eyes).
If you have any developed photo negatives lying around, the black strip at the end can be sliced into rectangles and glued onto kit periscopes. This material has apparent depth and is optically smooth, unlike glossy paint, which can pool at the edges or acquire specks of dust while drying. I haven't seen any really convincing way to depict the laser protected periscopes, though some builders use the metallic colored confetti sold at party shops.