uggggggh dirty glass.
I hate when people smoke out of dirty glass - It defeats the whole purpose. If you use alcohol before or after every smoke it takes 5 seconds to clean your pipe and if you are really into resin you can pour the dirty alcohol in a cereal bowl let it evaporate and smoke the nasty residue later.
If you want to see the colors change, clean your pipe, and smoke out of it. One sesh and you will see the colors change as the residue builds up. I have mostly clear pieces, but I still clean my color changing glass after every sesh.
There is nothing worse than having some nice green and pulling it through a nasty pipe with old water. I am shuddering now.
If you like the taste and smell of a dirty pipe, by all means continue. But once you smoke out of clean glass I can almost promise you that you will not go back to dirty glass.