How do I Paint mason jars a clear deep blue

https://www.hometalk.com/diy/decorate/rooms/paint-mason-jars-easily-with-less-mess-20128147

I believe that you are looking for cobalt blue glass. That color is in the molten glass before the jar is made. The entire furnace melt has to be that color and that could be as much as 500 tons. There are paints that can give a rough approximation but you will not get that same appearance. Sure would be cheaper if you could.

I would use a stained glass paint.

Hometalk has tons of posts for painting mason jars and vases. Click on the link below for ideas.

https://www.hometalk.com/search/posts?filter=Mason%20Jars