Is there a household method to decolorize potentially contaminated water?
A simple test you can do is to boil a large amount of the water and see if a sediment is left in the vessel. This will tell you certain things about you contaminant.


Is it particulate? We expect so because a filter is removing the contaminant.
Is it's boiling point below that of water?


If you get a residue what is it's state? I'm expecting a solid, I dont anticipate a coloured liquid that is miscible in water with a boiling point higher than water.


Does it burn? How does it burn? Colour of flame? Further residue?


I'd also try adding a colourless surfactant to the water, does it remain coloured?