Mod Version: 1.11.2-3.3.4.1

Forge Version: 1.11.2-forge1.11.2-13.20.0.2228

Description:
Running SEUS-v11.0 shaderpack using OptiFine_1.11.2_HD_U_B7, aurora bands are grey and opaque. Aurora has color and transparency when shaders are disabled.

Yep. Its the shader pack - it wants to own the rendering. Not all shader/packs do that. Not a bug.

Do you know a shaderpack that plays well with others?

I do not know of any "heavy" shader packs that play well. The built-in Minecraft shaders work well, but that may not be what you are looking for.

I will look around. Would you like me to post a follow-up comment here if I find one that is compatible?

Yes, please do.

Unfortunately, what SEUS provides is actually the best compatibility with your aurora out of the dozen shaderpacks I tested.

I tried a few and liked kuda-shaders - all the others gave me broken skies. But I'm not sure if I've seen an Aurora - gray or otherwise.

In my testing, anything based on Chocapic13's Shaders seemed to break completely on trying to render auroras.

Sildurs Shaders render aurora nice too

Pushed v3.4.9.3 with changes.

Same with BSL shader too.

Yep. Most if not all advanced shader packs will have this problem. It's a common issue and a lot of mods have similar problems.