The subject was mentioned in another thread by @adamhiram about whether to use colored backgrounds, gels, or both, rather then hijack his thread I started a new one. Another TPF member @Derrel put me on to Dean Collins and his "Chromozones" back a year or so ago. Basically by using adjustment to the reflective reading on the background you can change either white or black to represent the entire gray scale. Following this same method you can easily replicate an unlimited range of colors from a single gel. When I actually set up and practiced his methods I was shocked at how simple it was. First the video The system revolves around using a base reflective reading off the background of f/11 and a camera aperture of f/11. Obviously being limited with an aperture of f/11 isn't always feasible, so at the end he talks about a chart for adjusting lights, to match your aperture. You read down the center gray shaded column, to find the aperture you want to use. Then you read across (left or right) to get the reading you need to set your background lights at. Remember, the meter reading you take off the background is REFLECTIVE with the meter pointed toward the background. The chart is small and hard to read. I made a duplicate of it, that I keep handy for reference. You can find a PDF copy of the chart here Dean Collins Chromo Chart.pdf I also have created color charts for the gels I use regularly using the above chart so I can quickly create the exact color I want.