How can you match the color since it seems to change

For modern, anti-laser coated optics, I start by painting them black. Then I add two coats of stop light red clear. Once that dries, I add two coats of clear gloss. This allows the light to penetrate the clear red and reflect back, creating the appearance of different colors (red, purple, blue, gold, etc.) when viewed from different angles. I think it is effective and looks great, without looking like a red blob on the optic.

This is what I use... cheap and works great


https://www.youtube.com/watch?v=mnqDgQY3XKg

Here is what it look like on my M1A1

https://c1.staticflickr.com/3/2831/33167293461_466de92596.jpg

I use these. Simple to use, gives a nice prismatic look and are self-sticking.
https://store.spruebrothers.com/searchresults.asp?Search=reflection&Submit=

Use old film rolls from old cameras