It's obvious that, currently, we don't need bonfires for lighting. Just grab a netherrack or magma block and light it up.

My idea is a little different than that. Bonfires should be easier to get than Nether materials, something like a log smeared with coal or flint, basically just a slightly more luxurious torch. It functions exactly the same as Netherrack, and has a nice smoldering wood texture. That isn't the main function, though.

By adding dye to a bonfire block, players will be able to create 16 colors. When lit, the flames will match that color. I've found myself wanting to use colored flames many times in the past, especially aqua blue flames, green flames, or purple flames. As it currently stands, it's impossible to create things like World of Warcraft's Fel flames without retexturing the fire, and that should be changed to create more dynamic builds. The light doesn't even have to be colored, just the fire should be.