Is there any way to fix this? I'm using Optifine G7 for 1.16.5 and this happens on every shader

Please fill in the full template. Also, picture is broken

I can see it fine - it's optifine's fault, not ours

When changing shaders you have to reload entire mc, not sure if our fault or their, feel free to open at Optifine issue tracker - I tried haunting that down but no idea where it comes from

I've seen the same behavior just using the Internal Shader. I've been trying to use the ComplementaryShaders_3.07.zip or Internal and neither work. The same messed up image snipechan posted is also what I see when placing any building down. I've had to turn off shaders due to the incompatibility with them.

Internal shaders are currently not supported yes. General shaders are generally supported but they used to work fine in 1.16.5. if they're broken now, Optifine broke mod-compat and it's a "them issue".

I've come to terms with this optifine glitch and just turn my shaders off, put buildings up and back on. :D

Have you tried restarting entire mc after you've changed the shader?

Nope

Reopening for further investigation, also please send debug.log from session when you try opening building previews before + after shader change

well, it is very interesting that my Forge 36.0.55 with MineColonies 0.14.9-Alpha with Structurize 0.13.148-Alpha appear to now be working for Internal Shader pack and ComplimentaryShaders_3.07.zip. Didn't see any Optifine G7 option for shaders, so couldnt provide a screen shot for them even though it is part of the modpack I created for this server.
First image is Internal Shader

Second image is ComplimentaryShaders

it magically started working. Could have been fixed between Forge 36.0.28 and 36.0.55 (which is what I'm on) or a change in MineColonies corrected it. Will need @snipechan to confirm it works in whatever version he/she is running on.

So it still works when you restart mc after shaders change? or it works now without restarting?