It seems the current Hitech filters are giving a magenta cast. Old batches (2 years ago) are ok.
And there are better filters than the standard Lee ND and GND. Lee gives out a very slight color cast at times. The Lee pro glass series are better.
Singh-Ray are also quite good but very pricey.
The best, I heard, are Schneider optic's glass filters.
I am thinking of getting the LEE ND standard and am curious to find the quality standard between the pro glass and resin(colur cast). I was wondering if there is any images availble for comparison purpose