It all depends on what you want each light to accomplish. If it's used for visibility, then it needs to provide for accurate skin tones. This is why people use (I'm using
ROSCO as an example here only because I can name them off the top of my head.
Apollo,
Lee, and
GAM all make great
gel colors as well!) R64 light steel blue if they want a light blue that still maintains good skin tones, or R33 (
no Color Pink), or R51.
If you want a blue- do you want one with green wavelengths to give you an aquatic feel, or one that is a
neutral blue? or one that perhaps has a
red shift when dimmed? The way to find these things out is look at the wavelength shown on the
swatch book. This will tell you how much of the spectrum the
gel will transit. Something with a full(ish) spectrum will be good at
rendering colors and skin tones over all. Something which cuts out to ~0% at various wavelengths (a red for instance might have it's
line drop out in the ~500nm range to show that it doesn't transmit any green at all.) So if you shine this
gel on something that is green, the object will appear black or brownish.
Use a small flashlight and a
swatch book to see what the color looks like on clothing, skin, and the paint of the set, then choose the color that you think will help transform or accentuate those items in a positive way that helps the design and the director's
vision. Remember- It's okay to change your mind during tech. EVERYONE makes
gel mistakes sometimes. You think a color is going to be great and when it gets to tech suddenly it doesn't look how you thought it would in your mind. Ken Billington related that he once regelled an entire show on Broadway after opening and it fixed the entire show.
For shows like the tempest, and Midsummer Night's Dream- some of the best designs I've seen used super saturated color for downlight/backlight, and then subtle followspots on the actors (diffused) to "pull them out" of the colorful environment.
