MadHatAK is correct that you create data/minecraft/tags/blocks in your resources folder and add it there.
That's how datapacks override vanilla stuff.
Making a walls tag in your mod just creates your own walls tag with only your walls in it.
In your development environment, /data/minecraft/tags/blocks add your walls AND what minecraft has in their JSON. I had a similar problem and, this fixed it.
I'm not sure if this still works, but you might be able to cast the ILightReader to a World(do an instanceof check it can be null). Then if it is use World::getTileEntity and store your colors in the TileEntity.
Hi
Yeah that's me
I got all the breath weapon sounds from freesound.org- things like bunsen burners, ice cracking, wind, waterfalls. I did layer a few sounds together using Audacity but nothing complicated. I've found most of the samples on the site to be decent quality because they're usually submitted by enthusiasts with good quality recording gear. Plenty good enough for minecraft mods
Cheers
TGG