In the Bible, hell is described as a land of fire and brimstone. Brimstone is another name for sulfur, a yellow mineral that burns blue. So I propose the Brimstone Caverns biome for the nether. It would be fairly common, and instead of netherrack it would be made of brimstone, a brownish yellow stone with a similar texture to netherrack’s. Fire here is blue like on soul sand, and lava is blue as well. Brimstone itself can be crafted with nether bricks in the same recipe as red nether brick and it would make yellow nether brick. Instead of quartz, we have nether anthracite, a super fuel with three times the power of coal. In real life anthracite is a harder and more powerful form of coal, so it would look similar to coal but maybe with some bluish tint. Brimstone could also be used to craft a super furnace, which cooks everything 50% faster, and everything nether related 150% faster, such as nether quartz ore, netherrack, etc.
If you want backup for all the blue fire and lava and whatnot just search “Indonesian blue volcano” and you can see the beautiful blue lava flowing over the sulfur.