I remember the term we used on tanker pool when sampling the fuel 'clear and bright, free from shite' . AVTUR could come in many shades though, from gin clear to a straw colour. After visual sampling/water check with a detection capsule and syringe and specific gravity checks with a hydrometer and thermometer to see if the fuel was in density spec and not contaminated it could be issued to the aircraft. The first time I came across Cladosporium Resinae 'aka Gladys' was after I left the RAF and was driving a MAN artic which kept cutting out at random intervals. Fuel filter changed and same thing. I kept saying to the boss that it might be fuel related and there is an algae that can grow in fuel, nothing can grow in diesel he said but he wouldnt listen. He spent a lot of money on filters. Eventually they drained the fuel tank and out plopped what can only be described as the most disgusting mass of green/brown shite that ive ever seen. Never felt so smug