This usually means tannins, which are organics leached out of peat, leaf litter, or marshy ground near the well.

The color is dissolved rather than suspended, so it travels right through anything that works by straining particles out.

Look for an even tea or straw color that does not settle overnight, a faint earthy taste, and laundry that grays over time.

Do not buy a sediment filter for this. The water is not carrying particles, and a clean cartridge comes out the same color as the water.