FWIW, got curious about the comment that a 0.5 micron filter will remove the color. (This did not sound correct.) So. . . . we ran some through a 0.45 micron filter and guess what, still as red as ever. So we tried a 0.2 micron filter, still as red as ever. It is in solution, and cannot be filtered out, even the GCMS does not filter it out, just gives it a known peak and goes on. This issue also means that even if UV exposure will lessen the color, the chemical tracer still exist and that is what they have been making the proof on for the fines. The DOT has gotten far more detailed in looking for the red, they will fine for just a few PPM. Depending on the officer that is checking, even black fuel, from WMO, will get bad attention, even with a legit excuse.