Edit: Thank you iron-mage for pointing out that the green and black glass were broken lol, fixed the link and download ^-^
Edit2: I've added connected textures thanks to referencing the connected glass block pack by AnimeChips ! To see the textures connected as they are in Vanilla, you will need Optifine. However the pack still functions without it.

I am using the Mizunos Minecraft texture pack in all of my example images (very cool pack, I use it a lot, v aesthetic, recommend).

This was a quick pack I made for a friend that I figured would be useful enough to post, as I couldn't find any examples of similar packs when I was trying to make it lol.

This pack does a simple change to make colored glass block textures differ from glass panes. This is only noticeable when equipped above another texture pack and applies the vanilla glass textures to glass blocks but keeps the alternate texture pack's glass pane textures. For more specifics on how this works if you want to apply it in your own pack, see the bottom of the description.

This pack works without Optifine :D and again the Glass Blocks Fixed texture pack needs to be above the alternate texture pack for it to work (see the second screenshot to see what I mean).

Hope this helps people ^-^ I spent a couple harrowing hours on unhelpful reddit forums before I figured it out, pls appreciate my sacrifices lol


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How this Pack Works :>

For this explanation I will be using pink_stained_glass as the example, but it works for all the other colors obvi, am just using it so the wording is less confusing. If you're using this for your own pack, open up mine to follow along (I have learned everything I know about texture packs by stealing bits and pieces from other packs, so I highly recommend doing the same to make sure yours works, it's all good).

Mk so you need a blockstate file called "pink_stained_glass" (default file name) which references a model file with a new name (in my pack, that new name is "pink_stained_glass_side"). This new name can be whatever you want that makes sense.

Then your newly named model file "pink_stained_glass_side" goes somewher special :o Make a new folder in the [​models] folder called [​blocks] and put the model file "pink_stained_glass_side" inside. That file is a copy of the original vanilla model file, however the texture that it references (originally "pink_stained_glass") is now changed to "pink_stained_glass_side", the name of the texture you want the glass block to be.

Finally, in the textures folder there is a texture called "pink_stained_glass_side" with the vanilla pink stained glass texture, or whatever you want your glass block to look like.

That's all you need :> As for doing the reverse, specifically keeping the glass block texture of an alternate pack while referencing the vanilla glass for the panes,...you might need to make like 4 more model files but the idea is the same. The glass pane blockstate file references like 6 different models for when a pane is connected, a corner, a post, etc, so each model needs an alternate name, although they'd be able to reference the same texture in the model file. This is all speculatory, I haven't tested it, so if you're really stuck on it leme know and we can discuss it on discord or smth