Have a same problem with reflector on Meopta Meochrome color head.Can't have a good contrast because yellow metalic paint on reflector and it was like Y filter is always on.I have clean this yellow paint with fine sand paper until glass surface was mat.Glass surface must be mat because I have repaint reflector with aluminum heat resistance (600C) paint.It's cheap paint here in Croatia (0,2 l about 4$).I have paint reflector twice inside and twice outside and next day put reflector in the oven (200C) for about 20 min.Now you have nice silver heat absorbing color neutral reflector.Mixing chamber was repaint with white acrylic paint from hobby shop which is heat resistance (160-180C).Halogen bulb surface is about 250C.Because I have another color head (for parts) I have change Cyan filter with another Magenta and now there is 2 Magenta and 1 Yellow filter.With two Magenta on this color head it's possible to reach full contrast on any paper.