A couple of nights ago I watched the film "Stripes". One of my favorite comedies starring Bill Murray, the late John Candy, the late Harold Ramis, John Laroquette... Unfortunately this one is on Kodak SP stock and has faded. I used two different blue gel filters and, whilst there are some trade-offs when using these, I was pleased with how they worked. Some light wear on the print, decent sharpness but not pin sharp, but it is the uncut version....
The kit I bought from ebay was about $20 USD, and included a plastic lens cup where you can insert the lens gel(s)(fit to an Elmo 16mm lens size), and three different blue gel filters. There is another size available for Eiki too. I was using an Eiki projector and so used a bit of tape to keep the different lens size cup tight to the front of the objective.
Here are some pics....In lighter scenes, there was a bit of a bluish tinge to my eyes, as well as a bit less brightness, but again the 'win' was better overall colors...I would definitely recommend using the gel filters. Unfortunately, I didn't take a pic without the filters to show the 'Before' filter version....