All of the color in mine has gone away below the water line. It's just white now. I've been pretty religious about keeping the FC level inside the FC/CYA chart. I did SLAM once for 4 days with one overshoot but the fading started well after. It happened over about a month, or maybe three weeks. This is the 3rd year for the liner and first year for TFP. It had a few bleached spots from where shock granular settled on the bottom from years past before switching to TFP.
I'm not sure it's all bad. A solid white pool is kind of neat. But now I'm thinking of ways to dye the water. Using TFP, the water is so clear, I don't think I'll ever be able to keep that white bottom clean.