Black Teflon seals are PTFE with a carbon fill, this seal is a very good general purpose seal for any solvent.
Gold plunger seals are made of UHMW-PE (Ultra High Molecular Weight Polyenthylene) with fill that gives it a gold appearence. The seal provides good seal life and does not shed particles like that of other seals. The gold seal is insert to all common HPLC solvent mixes