That red/blue color is applied through an electrolytic process called anodizing. It also creates a corrosion and wear resistant surface layer.
It can be removed with Easy Off Oven Cleaner, or Crystal Drano dissolved in hot water. Either is very corrosive
BE SURE TO WEAR SAFETY GLASSES!
Something to think about... After the anodizing is removed the pieces will have no corrosion resistance. You should have them clear powdercoated or you will forever be polishing them.
Personally I like the colored fittings.
Rodger